Run-on is a term used to describe what happens when the key is turned
off and the engine continues to run somewhat erratically for a second or
two, or even quite some time. Run-on causes high loadings on piston
rings and has the potential to damage the engine, so should be addressed
as soon as possible, even if it is simply by stalling the engine with
the clutch until a more permanent fix is sorted.corteco auto oil seals.
Run-on is caused by the fuel spontaneously igniting in the absence of a
spark from the plugs. In turn, there are a number of factors which can
cause this spontaneous combustion. These causes are covered in a
general way on my page combustion problems and detonation while the
specific means of addressing it are outlined below.
In summary: B series engines – particularly the higher compression
ratio version – are susceptible to run-on as we all know, but if
everything is right most engines won’t do this . A few engines defy all
attempts but are nowhere near as bad if all the items set out below are
attended to.corteco auto oil seals.
No 1 cause:
Most cases of run-on in B’s are down to wear in the carburettor throttle
spindles, which allow air to leak in in varying quantities at idle and
small throttle openings. This causes the mixture to lean off when the
engine speed cuts after the key is turned off … and lean mixture is a
key pre-condition for spontaneous combustion.
Worn spindles can be easily detected by wiggling the throttle shaft to
see if there is any movement between the shaft and carb body – there
should be none. There is limited value in trying to address the run-on
by other means while wear is present in the spindles. Renewing the
spindles and (if required) their bushes is relatively simple and
inespensive, will fix the problem completely in 90% of cases, and will
also considerably improve the smoothness and consistency of the car’s
idle.
Other factors associated with the tuning:
Idle speed too high (should be 700RPM but worn carbs usually mean it
can’t idle that slow, producing a double whammee). This is the next
most important factor after the condition of the throttle
spindles.corteco auto oil seals.
Mixture too lean.
Incorrect ignition timing
Marginally cooler running N8Y spark plugs help offset the difference in
petrol as compared with the specified N9Y without any adverse effects on
other aspects of performance.
Cooling system
A relatively unusual thing to watch for is that sometimes there are
cases of mismatch between the cooling holes on the head. Some of the
very late B series heads had a different water jacket hole pattern on
the spark plug side. Fitting this to an earlier block will considerably
restrict cooling around the plugs and results in run-on, pinking and
even burnt plugs.
Petrol
Octane rating is important for combustion stability so has a big effect
on run-on. Any B series engines over 8:1 compression should not be
running 91 octane fuel. Even 95 octane petrol is marginal, the engine
works much better with 98.
Problem cases
In 95+% of cases, if the factors above are addressed the engine won’t
run-on. Some of the rest are simply coped with by depressing the clutch
when turning off the engine (the extra drag from the release bearing is
enough to make the difference).corteco auto oil seals.
However, a small number defy every attempt to eliminate run-on and I’ve
formed the view that this is due to the nature/placement of the cores
which formed the cooling jacket in the head affecting the efficiency of
cooling around the spark plugs and thus causing them to run a bit hot.
I’ve come to this conclusion based on the following observations:
Some heads won’t run-on at all even under adverse conditions such as a
modified head with very high compression and std cam timing.
Working very quickly, a fresh set of plugs is fitted to a warm engine,
if the engine is started and turned off immediately it doesn’t run-on,
but reverts to run-on if it runs for any longer than that.corteco auto oil seals.
Refitting the old plugs after they have cooled has the same result, so it appears down to the temperature of the plugs.
The occurrence seems related to the head – swap the head and the problem
goes. Put the head on another engine and that engine acquires
run-on.corteco oil seals.
Anti-run-on valves
An anti run-on valve solves persistent cases and make all others more
tolerant to incorrect set-up. This valve was never std for a B as far
as I know (I may be wrong but I’ve not seen it in any parts books) but
it was used in other vehicles like the Marina, and then later the Metro
when the compression got up to 10.5:1 std.
The valves are available, but quite expensive – certainly more expensive than any of the above.
If all else fails
As noted above, if run-on does occur, it is always better for the engine
to put it in gear and stall it with the clutch than allow it to
continue.corteco auto oil seals.
Friday, March 20, 2015
Audi corteco oil seals
Combustion problems caused by
erratic burning and/or detonation of fuel rather than controlled and
even burning shorten engine life and also cause losses in economy and/or
power. A number of terms are used to describe them, including
pinking, pinging, detonation. Audi corteco oil seals.There
are a number of causes, with low octane fuel and distributors not
performing to spec, especially wear in the centrifugal advance
mechanism, being the leading culprits.
While there are several types of combustion problem, they fall into two general categories of phenomena which are loosely described as detonation which are:
spontaneous combustion which occurs independently of the ignition spark (diesel action), and
pre-ignition, brought about by the spark occurring too soon.
Technically they are quite different phenomena, but sometimes they are linked. Some of the causes are common to both.Audi corteco oil seals.
For simplicity, the following doesn’t differentiate between the two, as to the untrained ear it can be hard to tell the difference.
Note: Run-on (engine continues to run – somewhat erratically – when the key is turned off) is a combustion problem which is covered in a separate page: Run on.
Combustion – how it should be:
The fuel/air mix in the combustion chamber is supposed to burn evenly rather than explode all at once, and should spread out from the spark plug at a steady rate across the chamber. A certain amount of swirl or turbulence in the fuel/air mix is needed to achieve this. If there is too much turbulence, instead of spreading evenly across the combustion chamber after the spark ignites the fuel, the last bit of fuel/air in the chamber can explode spontaneously … which we hear as pinking or detonation.Audi corteco oil seals.
Peak useful combustive effort is achieved when the spreading flame front reaches its peak pressure at 12 degrees after top dead centre. The point at which the spark appears is timed to achieve this. That the spark is timed to appear anything up to 30 degrees before TDC imdicates that it takes quite a bit of time (relatively speaking!) for the flame front to take in most of the fuel compared with it all detonating at once.Audi corteco oil seals.
For a given amount of turbulence, the speed of the flame front depends mainly on the pressure in the cylinder – the less pressure, the slower it burns. Hence at low pressure (high vacuum) the spark needs to be even earlier – and so you have a vacuum advance.Audi corteco oil seals.
Because the speed of the front is independent on engine speed, it is necessary to make the spark appear sooner (ie advance its timing) as the engine speed increases. At higher speeds, the cylinder doesn’t fill completely so the reduced pressure tends to offset the increase in engine speed. Because of this counterbalancing effect, the amount of advance needed doesn’t keep increasing, but instead reaches a maximum figure after which engine speed increase is fully offset by reduced filling.Audi corteco oil seals.
If the peak pressure is too late, then engery is wasted, mostly as heat going to the cooling system rather than as mechanical energy in the piston. If it is achieved too early, then most of the energy is pumped back into the moving piston, increasing its temperature and hammering it against the bore … once again, we hear this as pinking/detonation.Audi corteco oil seals.
While there are several types of combustion problem, they fall into two general categories of phenomena which are loosely described as detonation which are:
spontaneous combustion which occurs independently of the ignition spark (diesel action), and
pre-ignition, brought about by the spark occurring too soon.
Technically they are quite different phenomena, but sometimes they are linked. Some of the causes are common to both.Audi corteco oil seals.
For simplicity, the following doesn’t differentiate between the two, as to the untrained ear it can be hard to tell the difference.
Note: Run-on (engine continues to run – somewhat erratically – when the key is turned off) is a combustion problem which is covered in a separate page: Run on.
Combustion – how it should be:
The fuel/air mix in the combustion chamber is supposed to burn evenly rather than explode all at once, and should spread out from the spark plug at a steady rate across the chamber. A certain amount of swirl or turbulence in the fuel/air mix is needed to achieve this. If there is too much turbulence, instead of spreading evenly across the combustion chamber after the spark ignites the fuel, the last bit of fuel/air in the chamber can explode spontaneously … which we hear as pinking or detonation.Audi corteco oil seals.
Peak useful combustive effort is achieved when the spreading flame front reaches its peak pressure at 12 degrees after top dead centre. The point at which the spark appears is timed to achieve this. That the spark is timed to appear anything up to 30 degrees before TDC imdicates that it takes quite a bit of time (relatively speaking!) for the flame front to take in most of the fuel compared with it all detonating at once.Audi corteco oil seals.
For a given amount of turbulence, the speed of the flame front depends mainly on the pressure in the cylinder – the less pressure, the slower it burns. Hence at low pressure (high vacuum) the spark needs to be even earlier – and so you have a vacuum advance.Audi corteco oil seals.
Because the speed of the front is independent on engine speed, it is necessary to make the spark appear sooner (ie advance its timing) as the engine speed increases. At higher speeds, the cylinder doesn’t fill completely so the reduced pressure tends to offset the increase in engine speed. Because of this counterbalancing effect, the amount of advance needed doesn’t keep increasing, but instead reaches a maximum figure after which engine speed increase is fully offset by reduced filling.Audi corteco oil seals.
If the peak pressure is too late, then engery is wasted, mostly as heat going to the cooling system rather than as mechanical energy in the piston. If it is achieved too early, then most of the energy is pumped back into the moving piston, increasing its temperature and hammering it against the bore … once again, we hear this as pinking/detonation.Audi corteco oil seals.
Benz corteco oil seals
Wrong octane petrol for the
compression ratio. Higher octane petrol is more stable, so less inclined
to explode spontaneously. 96 octane will work up to 10:1 with ease if
everything else is right, even up to 12:1 has been possible with
modified squish and very careful set-up.Benz corteco oil seals.
Wrong advance rate (too much advance too soon) – with higher compression or lower octane fuel the engine will need less advance around 1500 – 2500 RPM, with about the same total advance at higher revs.
Too much squish for the compression ratio:
Squish (the squish of fuel/air trapped between the piston top and the bit of the head face which overlaps the bore and ejected with great speed into the combustion chamber as the piston gets to the top) is a design feature to inject the right amount of turbulence to get proper burning.Benz corteco oil seals.
Higher compression also promotes turbulence, so the general rule is that as the compression goes up the squish should go down. If you have an MGA1500 head on an MGB for example, the chamber volume is smaller (=higher compression) giving at the same time more squish due to the overlapping head face area being larger. Squish is further increased due to the bigger bore size. Benz corteco oil seals.So the result of combining all these will be most likely combustion irregularities
To limited extent, too much squish can be ameliorated by changes to the ignition timing, but the ideal solution is to reduce the squish whilst retaining the compression and then re-profiling the distributor.Benz corteco oil seals.
Inadequate cooling of the head, esp round the spark plugs. Check head gaskets for obscuring the coolant holes and that the hole pattern is the same in block and head. Check the casting in the water jacket around the spark plug holes for featuers which might reduce heat transmission to the water jacket.Benz corteco oil seals.
An alloy head works better in this respect but it would be an expensive way of curing detonation, and may not solve it at that – it depends where the problem is.
Wrong heat range spark plug. N9Y or equivalent is standard for 9:1 on 98 octane (what the engines were designed for). Cooler plugs may be needed for lower octane and/or higher compression. N8Y is good to use, above 10:1 it may be necessary to use N7Y.Benz corteco oil seals.
There is one remaining peculiar circumstance in which pinking can occur. If the engine has the wrong vacuum unit there is a distinctive symptom of pinking on part throttle which disappears or diminishes on full throttle. I have yet to find any other cause of this symptom (though there is always a first time!). (Refer to the page on vacuum units for a full explanation and diagnosis.)
Hot spots on the head from carbon or small machining dags (eg when the head is faced but the chamber edge is not radiused off where it meets the newly machined head face)
Even lean mixture can be a cause.Benz corteco oil seals.
Wrong advance rate (too much advance too soon) – with higher compression or lower octane fuel the engine will need less advance around 1500 – 2500 RPM, with about the same total advance at higher revs.
Too much squish for the compression ratio:
Squish (the squish of fuel/air trapped between the piston top and the bit of the head face which overlaps the bore and ejected with great speed into the combustion chamber as the piston gets to the top) is a design feature to inject the right amount of turbulence to get proper burning.Benz corteco oil seals.
Higher compression also promotes turbulence, so the general rule is that as the compression goes up the squish should go down. If you have an MGA1500 head on an MGB for example, the chamber volume is smaller (=higher compression) giving at the same time more squish due to the overlapping head face area being larger. Squish is further increased due to the bigger bore size. Benz corteco oil seals.So the result of combining all these will be most likely combustion irregularities
To limited extent, too much squish can be ameliorated by changes to the ignition timing, but the ideal solution is to reduce the squish whilst retaining the compression and then re-profiling the distributor.Benz corteco oil seals.
Inadequate cooling of the head, esp round the spark plugs. Check head gaskets for obscuring the coolant holes and that the hole pattern is the same in block and head. Check the casting in the water jacket around the spark plug holes for featuers which might reduce heat transmission to the water jacket.Benz corteco oil seals.
An alloy head works better in this respect but it would be an expensive way of curing detonation, and may not solve it at that – it depends where the problem is.
Wrong heat range spark plug. N9Y or equivalent is standard for 9:1 on 98 octane (what the engines were designed for). Cooler plugs may be needed for lower octane and/or higher compression. N8Y is good to use, above 10:1 it may be necessary to use N7Y.Benz corteco oil seals.
There is one remaining peculiar circumstance in which pinking can occur. If the engine has the wrong vacuum unit there is a distinctive symptom of pinking on part throttle which disappears or diminishes on full throttle. I have yet to find any other cause of this symptom (though there is always a first time!). (Refer to the page on vacuum units for a full explanation and diagnosis.)
Hot spots on the head from carbon or small machining dags (eg when the head is faced but the chamber edge is not radiused off where it meets the newly machined head face)
Even lean mixture can be a cause.Benz corteco oil seals.
BMW corteco oil seals
Check spark plugs are right heat range – examine for signs of overheating.BMW corteco oil seals.
Check carb needles are correct spec & not badly worn at the thick
end and that the mixture is not wildly out at idle. If the needle is
worn at the thick end, richen it up 2-3 flats on the adjuster and see if
that makes any difference to the detonation. If it does, buy new
needles.
Check compression ratio approximately using a compression tester. Roughly, every 20psi is 1 ratio. (Not 15psi as you’d expect since the process is adiabatic not isothermal – the air heats as it is compressed – and so the simple form of Boyles Law does not apply.) Now you know what you are working with.BMW corteco oil seals.
Check the ignition advance rate (see notes below) and adjust if necessary.BMW corteco oil seals.
I’d check where the advance is before doing anything. Re-profiling the advance curve very easy, and a lot easier and cheaper than removing the head, let alone replacing it. I’d always regard checking the advance curve as the first step. All that’s involved is measuring with a timing light what the timing is doing now (vacuum disconnected) and then tightening up the advance springs in the distributor a bit until it does what you want. In higher performance engines a spring change may be necessary, but not for what you are doing. Rough rule of thumb: 9:1 compression look for 25 deg total advance at 2000RPM and 30 deg after 2500 RPM, 10:1 compression no more than 20 deg total advance at 2000RPM reaching 30 deg after 3500 RPM.BMW corteco oil seals.
This is covered in more detail in Distributor advance rate adjustments – compensating for high mileage wear and for modified engines: Setting up ignition timing for modified engines.
If compression higher than standard, try one grade lower in spark plugs.
That’s the end of the simple checks, after that it’s a case of remove the head, check the squish area/chamber size/head type/cooling holes/hot spots etc.BMW corteco oil seals.
The later MGB heads had the same chamber capacity as the early MGB/MGA1622, but had a shallower chamber with less squish area; most had the same valve sizes, but some had bigger inlets so one of these would be the one to get if you could. Refer my web page B-series Cylinder head markings for notes on the various MGB heads.
Lowering the compression ratio is an option for addressing some of these problems. BMW corteco oil seals. However, I’d be reluctant to give away compression ratio as a cure to detonation – compression increases both power and economy. The B series engine functions perfectly happily on 9:1 to 9.5:1. 10:1 is very viable with a little care and setting the advance curve correctly and even 11:1 is reasonably comfortable on 96 octane if everything else is optimised.BMW corteco oil seals.
Check compression ratio approximately using a compression tester. Roughly, every 20psi is 1 ratio. (Not 15psi as you’d expect since the process is adiabatic not isothermal – the air heats as it is compressed – and so the simple form of Boyles Law does not apply.) Now you know what you are working with.BMW corteco oil seals.
Check the ignition advance rate (see notes below) and adjust if necessary.BMW corteco oil seals.
I’d check where the advance is before doing anything. Re-profiling the advance curve very easy, and a lot easier and cheaper than removing the head, let alone replacing it. I’d always regard checking the advance curve as the first step. All that’s involved is measuring with a timing light what the timing is doing now (vacuum disconnected) and then tightening up the advance springs in the distributor a bit until it does what you want. In higher performance engines a spring change may be necessary, but not for what you are doing. Rough rule of thumb: 9:1 compression look for 25 deg total advance at 2000RPM and 30 deg after 2500 RPM, 10:1 compression no more than 20 deg total advance at 2000RPM reaching 30 deg after 3500 RPM.BMW corteco oil seals.
This is covered in more detail in Distributor advance rate adjustments – compensating for high mileage wear and for modified engines: Setting up ignition timing for modified engines.
If compression higher than standard, try one grade lower in spark plugs.
That’s the end of the simple checks, after that it’s a case of remove the head, check the squish area/chamber size/head type/cooling holes/hot spots etc.BMW corteco oil seals.
The later MGB heads had the same chamber capacity as the early MGB/MGA1622, but had a shallower chamber with less squish area; most had the same valve sizes, but some had bigger inlets so one of these would be the one to get if you could. Refer my web page B-series Cylinder head markings for notes on the various MGB heads.
Lowering the compression ratio is an option for addressing some of these problems. BMW corteco oil seals. However, I’d be reluctant to give away compression ratio as a cure to detonation – compression increases both power and economy. The B series engine functions perfectly happily on 9:1 to 9.5:1. 10:1 is very viable with a little care and setting the advance curve correctly and even 11:1 is reasonably comfortable on 96 octane if everything else is optimised.BMW corteco oil seals.
Buick corteco oil seals
Twin carburettors have an unjustified reputation for being hard to keep in tune. Buick corteco oil seals.It’s
origins lie in the bad practice of fiddling with the carburettor of an
off-tune engine before having first checked that all else is in order –
compressions, ignition timing, distributor, advance rate, tappet
clearances, along with a lack of air leaks into the inlet manifold from
such sources as damaged gaskets or faulty brake servos.Buick corteco oil seals.
This is not clever regardless of whether you have one carburettor or several – the carb(s) should always be the LAST thing to adjust. However, typically, someone confronted with an out of tune twin carburettor engine readily recalls having heard that they are hard to tune and keep tuned, so assumes that’s where the problem is and sets about trying to adjust the carburettors to make the engine run better.Buick corteco oil seals.
As the problem was probably somewhere else, the tuning attempts are invariably doomed to failure and the engine finishes the exercise no better off than it started. “Gosh!” (to be polite!) exclaims the frustrated tuner, “It’s true! Twin carburettors ARE hard to tune!!!” And so the experience is relayed on to others and the myth is perpetuated.Buick corteco oil seals
The actual tuning procedure is quite simple: First, check that everything else is to spec (see above) – it is a complete waste of time trying to tune out a fault elsewhere by adjusting the carburettors. Next, if you haven’t had anything to do with the car before, check the condition of the carburettors – particularly wear in the throttle spindles and also the needle valves.
Air leaking through badly worn spindles will make the idle uneven and variable, and so more difficult to set since the amount of leaking air is not constant. If worn, fix the problem or expect only limited success in setting the carbs. Having done these key initial steps, following the standard tuning/balancing process outlined in the workshop manual will quickly bring the carbs into excellent balance.Buick corteco oil seals.
SU’s are at correct mixture when lifting the piston about 1-2 mm makes no difference to the idle speed (as described in the workshop manuals). If however you are measuring exhaust CO readings etc, they usually will be high, due to the siamesed inlet ports as much as anything, but also the lack of emulsified air in the droplets as they leave the jet. The readings clean up immediately the car is under load.
As the carbs get a bit of mileage, some wear does occur at the thick end of the needle, resulting in rich idle if the mixture is OK everywhere else, or weak mixture everywhere else if you set it correctly at idle. Simple solution: renew the jet needle. If the jet itself is looking oval, it will need replacing too.Buick corteco oil seals.
Having set the carbs up properly in this way (including renewing spindles etc if required), my experience with each car I have kept tuned over a period of more than twenty years is that only very minimal adjustment, usually none, is needed at subsequent tune-ups if everything else is set first. (Sorry to repeat it but it is vital).
If you don’t have ready access to a workshop manual, the tuning procedure itself is:
Adjust the throttle stops so each carb is sucking evenly (see below).
Adjust the mixture (also see below)
If there was significant adjustment needed for (2), repeat (1) & (2), or do a couple of loops through (1) & (2) if initial adjustment was major.
Adjust the linkages between carbs so that both carbs are taking up at the same time when the throttle is depressed. (Note: you should set the linkages up so that there is some free movement before the spindles start opening).
Check you are getting full throttle just as the pedal reaches full travel (so the cable doesn’t get stressed when the red mist sets in!) and adjust the cable and/or the return stop in the footwell if necessary to achieve this.The tuning is best done with air filters removed.Buick corteco oil seals.
This is not clever regardless of whether you have one carburettor or several – the carb(s) should always be the LAST thing to adjust. However, typically, someone confronted with an out of tune twin carburettor engine readily recalls having heard that they are hard to tune and keep tuned, so assumes that’s where the problem is and sets about trying to adjust the carburettors to make the engine run better.Buick corteco oil seals.
As the problem was probably somewhere else, the tuning attempts are invariably doomed to failure and the engine finishes the exercise no better off than it started. “Gosh!” (to be polite!) exclaims the frustrated tuner, “It’s true! Twin carburettors ARE hard to tune!!!” And so the experience is relayed on to others and the myth is perpetuated.Buick corteco oil seals
The actual tuning procedure is quite simple: First, check that everything else is to spec (see above) – it is a complete waste of time trying to tune out a fault elsewhere by adjusting the carburettors. Next, if you haven’t had anything to do with the car before, check the condition of the carburettors – particularly wear in the throttle spindles and also the needle valves.
Air leaking through badly worn spindles will make the idle uneven and variable, and so more difficult to set since the amount of leaking air is not constant. If worn, fix the problem or expect only limited success in setting the carbs. Having done these key initial steps, following the standard tuning/balancing process outlined in the workshop manual will quickly bring the carbs into excellent balance.Buick corteco oil seals.
SU’s are at correct mixture when lifting the piston about 1-2 mm makes no difference to the idle speed (as described in the workshop manuals). If however you are measuring exhaust CO readings etc, they usually will be high, due to the siamesed inlet ports as much as anything, but also the lack of emulsified air in the droplets as they leave the jet. The readings clean up immediately the car is under load.
As the carbs get a bit of mileage, some wear does occur at the thick end of the needle, resulting in rich idle if the mixture is OK everywhere else, or weak mixture everywhere else if you set it correctly at idle. Simple solution: renew the jet needle. If the jet itself is looking oval, it will need replacing too.Buick corteco oil seals.
Having set the carbs up properly in this way (including renewing spindles etc if required), my experience with each car I have kept tuned over a period of more than twenty years is that only very minimal adjustment, usually none, is needed at subsequent tune-ups if everything else is set first. (Sorry to repeat it but it is vital).
If you don’t have ready access to a workshop manual, the tuning procedure itself is:
Adjust the throttle stops so each carb is sucking evenly (see below).
Adjust the mixture (also see below)
If there was significant adjustment needed for (2), repeat (1) & (2), or do a couple of loops through (1) & (2) if initial adjustment was major.
Adjust the linkages between carbs so that both carbs are taking up at the same time when the throttle is depressed. (Note: you should set the linkages up so that there is some free movement before the spindles start opening).
Check you are getting full throttle just as the pedal reaches full travel (so the cable doesn’t get stressed when the red mist sets in!) and adjust the cable and/or the return stop in the footwell if necessary to achieve this.The tuning is best done with air filters removed.Buick corteco oil seals.
Chevrolet corteco oil seals
This can be measured on a
flow meter placed across the intake of the carb, or by listening (via a
hose but practiced ears don’t need one) to the level of suck at the
intake. If using a hose, make sure it is held at the same point relative
to the intake of each carb. Any difference in noise level not
discernable by the ear is not worth worrying about.Chevrolet corteco oil seals.
Mixture adjustment on SU carburettors
Note: This must be done after balancing the flow, as there is transfer between the ports via the balance pipe in the manifold, and if the flow in the carbs is not about even, there will be a major effect on the opposite port when adjusting any given carb.
Adjustment mechanism
There are two means of adjusting the mixture on SU’s originally fitted to most MG’s, depending on carburettor type:
The H and HS type of carburettor fitted to prior to about 1972 have an adjusting nut underneath the carburettor, around the base of the jet.Chevrolet corteco oil seals.
The HIF carbuerttor fitted to MGB’s from about 1972 onwards adjustment is via a recessed screw in the side of the carb body, quite low down and at about 45 degrees to the main throat of the carburettor.
(Note that post 1972 Midgets retained the HS type, and that the change-over period was 1972-74 for the MGB so either type could be fitted to these years. The HIF does not have a separate bowl, instead it is underneat the carb, incorporated into the body.)Chevrolet corteco oil seals.
Checking mixture strength
Lift the piston about 1/16” (either via the piston lifter on the carb body, or with a screwdriver or other probe small enough to not disturb the air flow into the carb.) Correct mixture is when the engine speed doesn’t change or increases a little then settles back to where it was. If the engine speed reduces the mixture is lean, if it increases the mixture is rich.Chevrolet corteco oil seals.
This is the only reliable way to set the mixture, though you can get it roughly there by screwing the adjuster in and out till it maximises idle. However, it still pays to do the last bit by piston-lifting.
This entry was posted in Engine – Tuning, MGA-MGB, Midget. Bookmark the permalink.Chevrolet corteco oil seals.
Mixture adjustment on SU carburettors
Note: This must be done after balancing the flow, as there is transfer between the ports via the balance pipe in the manifold, and if the flow in the carbs is not about even, there will be a major effect on the opposite port when adjusting any given carb.
Adjustment mechanism
There are two means of adjusting the mixture on SU’s originally fitted to most MG’s, depending on carburettor type:
The H and HS type of carburettor fitted to prior to about 1972 have an adjusting nut underneath the carburettor, around the base of the jet.Chevrolet corteco oil seals.
The HIF carbuerttor fitted to MGB’s from about 1972 onwards adjustment is via a recessed screw in the side of the carb body, quite low down and at about 45 degrees to the main throat of the carburettor.
(Note that post 1972 Midgets retained the HS type, and that the change-over period was 1972-74 for the MGB so either type could be fitted to these years. The HIF does not have a separate bowl, instead it is underneat the carb, incorporated into the body.)Chevrolet corteco oil seals.
Checking mixture strength
Lift the piston about 1/16” (either via the piston lifter on the carb body, or with a screwdriver or other probe small enough to not disturb the air flow into the carb.) Correct mixture is when the engine speed doesn’t change or increases a little then settles back to where it was. If the engine speed reduces the mixture is lean, if it increases the mixture is rich.Chevrolet corteco oil seals.
This is the only reliable way to set the mixture, though you can get it roughly there by screwing the adjuster in and out till it maximises idle. However, it still pays to do the last bit by piston-lifting.
This entry was posted in Engine – Tuning, MGA-MGB, Midget. Bookmark the permalink.Chevrolet corteco oil seals.
Citroen corteco oil seals
The vacuum unit works to
advance the spark on part throttle in order to improve efficiency and
fuel economy when cruising/at steady speed.Citroen corteco oil seals.
At full throttle the manifold vacuum disappears and so the vacuum unit
gives no advance. Hence it can be seen why a vacuum unit which advances
too far/too soon will give the very distinctive symptom of pinking on
part throttle which disappears or diminishes on full throttle.
Note: Sometimes owners are unaware that this is the case, as they (wisely) back off the throttle at the onset of pinking to reduce engine damage. For diagnosis, you need to grit your teeth and put your foot to the floor to see whether the pinking gets worse (in which case it caused by the mechanical advance) or disappears (the cause will be the vacuum advance unit) or remains but reduces (both).Citroen corteco oil seals.
If this test reveals that vacuum advance is the cause, by far the most common reason this is the case is when the vacuum unit has been replaced in the past with a wrong spec (but identical looking) second hand one – usually from a Mini. Mini ones advance further and sooner than an MGB one. The test to confirm is to disconnect the vacuum unit and see if the problem goes.Citroen corteco oil seals.
The vacuum unit specs are marked on it. 25D distributors (the ones with the knurled adjustment knob fitted up to about 1972-73) have these markings around the neck where the vacuum tube from the carb attaches. There are three 1 or 2 digit numbers separated by dashes, for example the MGB is 5-13-10. Citroen corteco oil seals.The first figure is the vacuum at which the unit starts to advance, the second is the vacuum at which the unit finishes advancing (both in inches of mercury) while the third figure is the distributor advance in degrees. Thus the vacuum advance on the MGB 25 D distributor:
Starts at 5 inches of mercury
Reaches its maximum advance at 13 inches of mercury
Has a maximum advance of 10 degrees at the distributor (which is 20 deg at the crank of course)Citroen corteco oil seals.
The vacuum advance specs your car should have are given in its workshop manual. This problem is confined almost exclusively to MGB’s with 25D distributors as these had quite a lot if initial mechanical advance compared with A series engines and later MGB’s.
(Note however that replacement distributors are all 45D, some of which are to the same specs as the 25D.)
Any remaining pinking should be followed up as described on the detonation and combustion pages.Citroen corteco oil seals.
Note: Sometimes owners are unaware that this is the case, as they (wisely) back off the throttle at the onset of pinking to reduce engine damage. For diagnosis, you need to grit your teeth and put your foot to the floor to see whether the pinking gets worse (in which case it caused by the mechanical advance) or disappears (the cause will be the vacuum advance unit) or remains but reduces (both).Citroen corteco oil seals.
If this test reveals that vacuum advance is the cause, by far the most common reason this is the case is when the vacuum unit has been replaced in the past with a wrong spec (but identical looking) second hand one – usually from a Mini. Mini ones advance further and sooner than an MGB one. The test to confirm is to disconnect the vacuum unit and see if the problem goes.Citroen corteco oil seals.
The vacuum unit specs are marked on it. 25D distributors (the ones with the knurled adjustment knob fitted up to about 1972-73) have these markings around the neck where the vacuum tube from the carb attaches. There are three 1 or 2 digit numbers separated by dashes, for example the MGB is 5-13-10. Citroen corteco oil seals.The first figure is the vacuum at which the unit starts to advance, the second is the vacuum at which the unit finishes advancing (both in inches of mercury) while the third figure is the distributor advance in degrees. Thus the vacuum advance on the MGB 25 D distributor:
Starts at 5 inches of mercury
Reaches its maximum advance at 13 inches of mercury
Has a maximum advance of 10 degrees at the distributor (which is 20 deg at the crank of course)Citroen corteco oil seals.
The vacuum advance specs your car should have are given in its workshop manual. This problem is confined almost exclusively to MGB’s with 25D distributors as these had quite a lot if initial mechanical advance compared with A series engines and later MGB’s.
(Note however that replacement distributors are all 45D, some of which are to the same specs as the 25D.)
Any remaining pinking should be followed up as described on the detonation and combustion pages.Citroen corteco oil seals.
Fiat corteco oil seals
Maintaining the correct valve
clearance is important to prevent premature valve train wear. Too
tight and there is a risk that the valves won’t seat properly and burn
out, too loose and the valve train will hammer itself to death.Fiat corteco oil seals.
The latter happens because the clearance is taken up past the end of the opening ramp if there is too much clearance. The valves don’t open and close at steady speeds, but rather start slowly then accelerate hard, followed by a period of gradual deceleration as the valve approaches full lift. (Closing works backwards through this sequence) There is a part of the cam lobe, the opening ramp, which causes the initial lift speed to be low and constant-ish to allow the clearance to be taken up without hammering. There is also a closing ramp to avoid the valve crashing into its seat. (Valve bounce occurs when the cam is rotating so fast that the springs can’t keep the followers in contact with the cam so instead of being eased back on to the seat the valve hits it at high speed).Fiat corteco oil seals.
Ramps on original BMC cams usually finished at about 11 thou on the cam side, that’s 13.5 thou at the valves on std A series rockers, 15 thou on std B series rockers. After the ramp, acceleration is rapid so the further you are off the end the worse the effect gets.Fiat corteco oil seals.
If you have a sliding fit on the right size feeler but can’t get the next one in, you’ll be safely on the ramp provided your rockers don’t have any wear indentations where they contact the valve (most feelers are wider than the indentation and so bridge it, giving a false reading). If you have deep indentations here you should remove the rocker gear and get the rockers refaced.Fiat corteco oil seals.
I have generally set clearances on road cars a bit tighter than spec: one thou tighter on A series, 2 thou on B series (due to the official B series clearance being right at the end of the ramp) so that any gradual valve train wear (up to a couple of thou over the recommended interval) between adjustment checks won’t take it past the ramp. I have not observed any ill effects on valve or seat life on the engines I’ve had long term, including those with fast road cams and driven enthusiastically.Fiat corteco oil seals.
There can be a small performance upside of running extra clearance, but for longevity of the valve gear (especially the 1275 cam followers which require engine removal to change) I have always opened clearances a couple of thou just for specific events when every little bit helps then reset afterwards.Fiat corteco oil seals.
The latter happens because the clearance is taken up past the end of the opening ramp if there is too much clearance. The valves don’t open and close at steady speeds, but rather start slowly then accelerate hard, followed by a period of gradual deceleration as the valve approaches full lift. (Closing works backwards through this sequence) There is a part of the cam lobe, the opening ramp, which causes the initial lift speed to be low and constant-ish to allow the clearance to be taken up without hammering. There is also a closing ramp to avoid the valve crashing into its seat. (Valve bounce occurs when the cam is rotating so fast that the springs can’t keep the followers in contact with the cam so instead of being eased back on to the seat the valve hits it at high speed).Fiat corteco oil seals.
Ramps on original BMC cams usually finished at about 11 thou on the cam side, that’s 13.5 thou at the valves on std A series rockers, 15 thou on std B series rockers. After the ramp, acceleration is rapid so the further you are off the end the worse the effect gets.Fiat corteco oil seals.
If you have a sliding fit on the right size feeler but can’t get the next one in, you’ll be safely on the ramp provided your rockers don’t have any wear indentations where they contact the valve (most feelers are wider than the indentation and so bridge it, giving a false reading). If you have deep indentations here you should remove the rocker gear and get the rockers refaced.Fiat corteco oil seals.
I have generally set clearances on road cars a bit tighter than spec: one thou tighter on A series, 2 thou on B series (due to the official B series clearance being right at the end of the ramp) so that any gradual valve train wear (up to a couple of thou over the recommended interval) between adjustment checks won’t take it past the ramp. I have not observed any ill effects on valve or seat life on the engines I’ve had long term, including those with fast road cams and driven enthusiastically.Fiat corteco oil seals.
There can be a small performance upside of running extra clearance, but for longevity of the valve gear (especially the 1275 cam followers which require engine removal to change) I have always opened clearances a couple of thou just for specific events when every little bit helps then reset afterwards.Fiat corteco oil seals.
Ford corteco oil seals
The most common cause of
combustion problems such as pinking in MG engines is not fuel as usually
assumed (provided the engine is running on minimum 95 octane), but
distributors not performing to spec, especially wear in the centrifugal
advance mechanism of the distributor.Ford corteco oil seals . This slackness results in the distributor giving too much advance too soon with obvious results.
Often this is “tuned out” by simply retarding the whole distributor, a move which certainly stops the pinking but also leaves insufficient advance at mid to high engine speeds – leaving the engine well down on power and sluggish. Even setting the advance to the correct spec using a timing light at idle doesn’t solve it, as the distributor has already used up most of its advance at idle when worn like this and so will end up well short of where it should be at mid-high speeds.Ford corteco oil seals .
In the following example to illustrate what to do, I have used pre-73 MGB’s as an example as they are one of the worst culprits. However, all cars with old distributors will experience wear changes the advance rate and adversely affects both power and economy. Although what follows is for the early B, the principle is the same for most distributors – only the actual advance specifcations will vary, the procedure remains the same.Ford corteco oil seals .
The specifications you will need are the static, idle, maximum and intermediate advance figures. These can be found in the workshop manual. Key points in interpreting this data are:
Remember to identify whether the specs are referring to crankshaft or distributor degrees – timing figures are usually crankshaft degrees, but advance figures can be given in either.Ford corteco oil seals .
The advance figures given in the manual are the amount of advance caused only by the distributor. To get total advance you need to add to this figure the static advance. In our example, the MGB manual lists:
static advance as 10 degrees
maximum advance as 20 crankshaft degrees
-so the total maximum advance is 10 (from the static setting)+20 (from the distributor) = 30 degrees. The total intermediate advance figures are worked out in a similar way. In our example, the book lists the advance at 1500 RPM as being 15 degrees, so the total advance at 1500 RPM will be 25 degrees.Ford corteco oil seals .
Start off confirming the problem by first checking the advance rate of the distributor as it is. Using our example, we set the advance at idle to the factory speified 14 deg, then checking the advance at 2500 RPM with a timing light (vacuum disconnected) – it should be 30 degrees total. It should drop steadily through 23-24 deg @ 1750 RPM to 14 deg at 700 RPM. If it doesn’t meet this within a degree or so at each speed (many can be 10 deg or more out) the only cure is to strip the distributor and rectify the advance.Ford corteco oil seals .
Often this is “tuned out” by simply retarding the whole distributor, a move which certainly stops the pinking but also leaves insufficient advance at mid to high engine speeds – leaving the engine well down on power and sluggish. Even setting the advance to the correct spec using a timing light at idle doesn’t solve it, as the distributor has already used up most of its advance at idle when worn like this and so will end up well short of where it should be at mid-high speeds.Ford corteco oil seals .
In the following example to illustrate what to do, I have used pre-73 MGB’s as an example as they are one of the worst culprits. However, all cars with old distributors will experience wear changes the advance rate and adversely affects both power and economy. Although what follows is for the early B, the principle is the same for most distributors – only the actual advance specifcations will vary, the procedure remains the same.Ford corteco oil seals .
The specifications you will need are the static, idle, maximum and intermediate advance figures. These can be found in the workshop manual. Key points in interpreting this data are:
Remember to identify whether the specs are referring to crankshaft or distributor degrees – timing figures are usually crankshaft degrees, but advance figures can be given in either.Ford corteco oil seals .
The advance figures given in the manual are the amount of advance caused only by the distributor. To get total advance you need to add to this figure the static advance. In our example, the MGB manual lists:
static advance as 10 degrees
maximum advance as 20 crankshaft degrees
-so the total maximum advance is 10 (from the static setting)+20 (from the distributor) = 30 degrees. The total intermediate advance figures are worked out in a similar way. In our example, the book lists the advance at 1500 RPM as being 15 degrees, so the total advance at 1500 RPM will be 25 degrees.Ford corteco oil seals .
Start off confirming the problem by first checking the advance rate of the distributor as it is. Using our example, we set the advance at idle to the factory speified 14 deg, then checking the advance at 2500 RPM with a timing light (vacuum disconnected) – it should be 30 degrees total. It should drop steadily through 23-24 deg @ 1750 RPM to 14 deg at 700 RPM. If it doesn’t meet this within a degree or so at each speed (many can be 10 deg or more out) the only cure is to strip the distributor and rectify the advance.Ford corteco oil seals .
Honda corteco oil seals
Most of the time the problem
is only a bit of wear in the secondary spring hook and/or its supporting
pins, allowing the distributor to advance too far before the second
spring takes up. The primary spring is seldom a problem in the MGB as it
is under constant tension when the car is running (and so doesn’t
chatter around the take-up point) and is also much lighter.Honda corteco oil seals.
Check the take-up point of the heavier spring – in our MGB example: when the heavier spring takes up, the cam should have moved about 1/3 of the way to its stop when the heavy spring takes up. Typically, in most worn MGB distributors the cam will advance nearly all the way before the larger spring cuts in!Honda corteco oil seals.
For other engines, you can work out the correct take-up point of the second spring by plotting the intermediate advance figures on a graph. Where the graph line changes gradient is where the second spring should take up. Work out what proportion of maximum advance is taken up at this point, and that’s the proportion the distributor cam should have moved towards its stop when the second spring takes up.Honda corteco oil seals.
New distributor springs are not available, but the problem is not insurmountable. Although the springs do lose a bit of strength with age/use, this is relatively insignificant compared with the additional advance generated by the wear in the spring hook and post.Honda corteco oil seals.
It’s easy to fix: It can be 90% cured simply and cheaply by closing up the hook on the heavier spring a bit so that it takes up at the correct point. To compensate for the normal amount of weakness in the secondary spring of a high mileage MGB, over-tighten the spring a little further. I usually close the hook up so that it takes up after one third of the cam’s movement from fully backed off to where it hits the stop. This is a degree earlier than original and gives a good approximation to the overall shape of the std advance curve with the average high mileage distributor.Honda corteco oil seals.
Closing the hook up is a bit fiddly: I grip the base of the hook (where it joins the main coil of the spring) in the corner of a vice, then tap the hook end-on with a small hammer.
Modified engines may require stronger springs to slow down the rate of advance (refer to the page on Setting up ignition timing for modified engines.) If the distributor springs are not strong enough, a stronger spring can be obtained from another Lucas 25D distributor. All BMC cars of the period had the same basic distributor, but varied in the spring strength and the point at which the secondary spring takes up. Suitable candidates are Mini or BMC1100/1300.
Once you have attended to the springs, install the distributor, reset the ignition timing & check the newly adjusted advance with the light again, followed by any final adjustments necessary from road test. You won’t believe its the same car after that!Honda corteco oil seals.
Check the take-up point of the heavier spring – in our MGB example: when the heavier spring takes up, the cam should have moved about 1/3 of the way to its stop when the heavy spring takes up. Typically, in most worn MGB distributors the cam will advance nearly all the way before the larger spring cuts in!Honda corteco oil seals.
For other engines, you can work out the correct take-up point of the second spring by plotting the intermediate advance figures on a graph. Where the graph line changes gradient is where the second spring should take up. Work out what proportion of maximum advance is taken up at this point, and that’s the proportion the distributor cam should have moved towards its stop when the second spring takes up.Honda corteco oil seals.
New distributor springs are not available, but the problem is not insurmountable. Although the springs do lose a bit of strength with age/use, this is relatively insignificant compared with the additional advance generated by the wear in the spring hook and post.Honda corteco oil seals.
It’s easy to fix: It can be 90% cured simply and cheaply by closing up the hook on the heavier spring a bit so that it takes up at the correct point. To compensate for the normal amount of weakness in the secondary spring of a high mileage MGB, over-tighten the spring a little further. I usually close the hook up so that it takes up after one third of the cam’s movement from fully backed off to where it hits the stop. This is a degree earlier than original and gives a good approximation to the overall shape of the std advance curve with the average high mileage distributor.Honda corteco oil seals.
Closing the hook up is a bit fiddly: I grip the base of the hook (where it joins the main coil of the spring) in the corner of a vice, then tap the hook end-on with a small hammer.
Modified engines may require stronger springs to slow down the rate of advance (refer to the page on Setting up ignition timing for modified engines.) If the distributor springs are not strong enough, a stronger spring can be obtained from another Lucas 25D distributor. All BMC cars of the period had the same basic distributor, but varied in the spring strength and the point at which the secondary spring takes up. Suitable candidates are Mini or BMC1100/1300.
Once you have attended to the springs, install the distributor, reset the ignition timing & check the newly adjusted advance with the light again, followed by any final adjustments necessary from road test. You won’t believe its the same car after that!Honda corteco oil seals.
rubber auto oil seals Porsche
There are two faults which show up in the breather systems of Midgets
and MGBs which cause dramatic oil consumption and lots of blue smoke,
even with a reconditioned engine. rubber auto oil seals
Porsche.Quite a number of engines have been unnecessarily reconditioned
because of these faults so if you have a smoky engine, although the
odds are that it does need overhaul, check these out before you dive in
and spend lots of money:
First miracle cure:
The breather pollution control valve on the manifold, where fitted, (approx 1964 to 1969-70 – 18GA, 18GB, 18GD MGB engines, 10CC, 12CC and early 12CE Midget engines) can develop a leak which allows the crank case to be significantly vented to the inlet manifold under high vacuum rather than only under full-ish throttle conditions when the manifold pressure is much closer to atmospheric. The result is that the strong vacuum sucks furiously at the crankcase, scavenging neat oil as well as the intended fumes into the inlet system. Hence oil combustion and blue smoke!rubber auto oil seals Porsche.
The valve is readily identifiable: It is attached to the middle of the inlet manifold and has a flat circular top of about 3” diameter. A hose joins the outlet (points towards the front of the car) to the breather on the side of the block.
To confirm the diagnosis: remove the PCV valve but leave the hose which joined it to the manifold in place. Block this hole off with a suitable bolt or whatever, and road test to see if the problem has gone.
Many an engine has been needlessly overhauled because of failure to check this out!
Replacing the diaphragm, or if necessary the whole valve (depending on the nature of the fault) will fix the problem in 10 minutes.rubber auto oil seals Porsche.
Warning: While it is tempting and much cheaper to simply vent the breather to atmosphere, doing so makes the engine more likely to leak oil – particularly if it is an A series Midget or 3 bearing MGB. The reason for this is that in its operation the breather maintains a small partial vacuum in the crankcase, which works against oil getting pushed out of the seals (or the rear scroll in the case of the 3 brg B & A series). Venting to atmosphere achieves the reverse effect – it maintains a small residual pressure inside the crankcase (it won’t be much, but without any pressure difference at all there would be no outward flow through the breather).
The partial vacuum system is used by all cars now and is one of the reasons modern engines don’t leak oil.
The other miracle cure:
The breather oil separator on the engine can become blocked, in which case simply cleaning it out solves the oil consumption problem.rubber auto oil seals Porsche.
This unit is incorporated in the front pushrod cover on MGB’s, while on 1275 Midgets it is attached to the timing chain cover. (Sorry, the 10CC engine’s arrangement has slipped my memory at the moment but it will be one or the other of these two).
There were two versions of the pushrod cover separator, the early one had a row of small-ish holes along the botom of the inside face while the later one had a much larger hole about 1.5 – 2″ square-ish at the rear end of this face.
It is the small hole version of the pushrod cover separator which is most prone to blocking up.rubber auto oil seals Porsche.
As described by Robert Paterson:
“Well, I’ve found the answer at last! Last week I took off the “side cover with separator” and it was just as you said, with small holes along the bottom. I could blow through it ok, so it was not blocked.
I decided to drill out the holes to a bigger size. When doing this, I found that it was full of very black goo! In fact, it took me three days to remove the goo – 37 years of old thick solid oil.
I fitted it back on the car and off we went with no problems – no more blue smoke! In fact, the motor seems to be a lot better and more alive, if you know what I mean.”
A simple way to address the gunge is to get an engine reconditioner to put in the cleaning tank.rubber auto oil seals Porsche.
First miracle cure:
The breather pollution control valve on the manifold, where fitted, (approx 1964 to 1969-70 – 18GA, 18GB, 18GD MGB engines, 10CC, 12CC and early 12CE Midget engines) can develop a leak which allows the crank case to be significantly vented to the inlet manifold under high vacuum rather than only under full-ish throttle conditions when the manifold pressure is much closer to atmospheric. The result is that the strong vacuum sucks furiously at the crankcase, scavenging neat oil as well as the intended fumes into the inlet system. Hence oil combustion and blue smoke!rubber auto oil seals Porsche.
The valve is readily identifiable: It is attached to the middle of the inlet manifold and has a flat circular top of about 3” diameter. A hose joins the outlet (points towards the front of the car) to the breather on the side of the block.
To confirm the diagnosis: remove the PCV valve but leave the hose which joined it to the manifold in place. Block this hole off with a suitable bolt or whatever, and road test to see if the problem has gone.
Many an engine has been needlessly overhauled because of failure to check this out!
Replacing the diaphragm, or if necessary the whole valve (depending on the nature of the fault) will fix the problem in 10 minutes.rubber auto oil seals Porsche.
Warning: While it is tempting and much cheaper to simply vent the breather to atmosphere, doing so makes the engine more likely to leak oil – particularly if it is an A series Midget or 3 bearing MGB. The reason for this is that in its operation the breather maintains a small partial vacuum in the crankcase, which works against oil getting pushed out of the seals (or the rear scroll in the case of the 3 brg B & A series). Venting to atmosphere achieves the reverse effect – it maintains a small residual pressure inside the crankcase (it won’t be much, but without any pressure difference at all there would be no outward flow through the breather).
The partial vacuum system is used by all cars now and is one of the reasons modern engines don’t leak oil.
The other miracle cure:
The breather oil separator on the engine can become blocked, in which case simply cleaning it out solves the oil consumption problem.rubber auto oil seals Porsche.
This unit is incorporated in the front pushrod cover on MGB’s, while on 1275 Midgets it is attached to the timing chain cover. (Sorry, the 10CC engine’s arrangement has slipped my memory at the moment but it will be one or the other of these two).
There were two versions of the pushrod cover separator, the early one had a row of small-ish holes along the botom of the inside face while the later one had a much larger hole about 1.5 – 2″ square-ish at the rear end of this face.
It is the small hole version of the pushrod cover separator which is most prone to blocking up.rubber auto oil seals Porsche.
As described by Robert Paterson:
“Well, I’ve found the answer at last! Last week I took off the “side cover with separator” and it was just as you said, with small holes along the bottom. I could blow through it ok, so it was not blocked.
I decided to drill out the holes to a bigger size. When doing this, I found that it was full of very black goo! In fact, it took me three days to remove the goo – 37 years of old thick solid oil.
I fitted it back on the car and off we went with no problems – no more blue smoke! In fact, the motor seems to be a lot better and more alive, if you know what I mean.”
A simple way to address the gunge is to get an engine reconditioner to put in the cleaning tank.rubber auto oil seals Porsche.
rubber auto oil seals Hyundai
The vacuum unit works to
advance the spark on part throttle in order to improve efficiency and
fuel economy when cruising/at steady speed. At full throttle the
manifold vacuum disappears and so the vacuum unit gives no advance.
rubber auto oil seals Hyundai.Hence
it can be seen why a vacuum unit which advances too far/too soon will
give the very distinctive symptom of pinking on part throttle which
disappears or diminishes on full throttle.
Note: Sometimes owners are unaware that this is the case, as they (wisely) back off the throttle at the onset of pinking to reduce engine damage. For diagnosis, you need to grit your teeth and put your foot to the floor to see whether the pinking gets worse (in which case it caused by the mechanical advance) or disappears (the cause will be the vacuum advance unit) or remains but reduces (both).rubber auto oil seals Hyundai.
If this test reveals that vacuum advance is the cause, by far the most common reason this is the case is when the vacuum unit has been replaced in the past with a wrong spec (but identical looking) second hand one – usually from a Mini. Mini ones advance further and sooner than an MGB one. The test to confirm is to disconnect the vacuum unit and see if the problem goes.rubber auto oil seals Hyundai.
The vacuum unit specs are marked on it. 25D distributors (the ones with the knurled adjustment knob fitted up to about 1972-73) have these markings around the neck where the vacuum tube from the carb attaches. There are three 1 or 2 digit numbers separated by dashes, for example the MGB is 5-13-10. rubber auto oil seals Hyundai.The first figure is the vacuum at which the unit starts to advance, the second is the vacuum at which the unit finishes advancing (both in inches of mercury) while the third figure is the distributor advance in degrees. Thus the vacuum advance on the MGB 25 D distributor:
Starts at 5 inches of mercury
Reaches its maximum advance at 13 inches of mercury
Has a maximum advance of 10 degrees at the distributor (which is 20 deg at the crank of course)
The vacuum advance specs your car should have are given in its workshop manual. This problem is confined almost exclusively to MGB’s with 25D distributors as these had quite a lot if initial mechanical advance compared with A series engines and later MGB’s.rubber auto oil seals Hyundai.
(Note however that replacement distributors are all 45D, some of which are to the same specs as the 25D.)
Any remaining pinking should be followed up as described on the detonation and combustion pages.rubber auto oil seals Hyundai.
Note: Sometimes owners are unaware that this is the case, as they (wisely) back off the throttle at the onset of pinking to reduce engine damage. For diagnosis, you need to grit your teeth and put your foot to the floor to see whether the pinking gets worse (in which case it caused by the mechanical advance) or disappears (the cause will be the vacuum advance unit) or remains but reduces (both).rubber auto oil seals Hyundai.
If this test reveals that vacuum advance is the cause, by far the most common reason this is the case is when the vacuum unit has been replaced in the past with a wrong spec (but identical looking) second hand one – usually from a Mini. Mini ones advance further and sooner than an MGB one. The test to confirm is to disconnect the vacuum unit and see if the problem goes.rubber auto oil seals Hyundai.
The vacuum unit specs are marked on it. 25D distributors (the ones with the knurled adjustment knob fitted up to about 1972-73) have these markings around the neck where the vacuum tube from the carb attaches. There are three 1 or 2 digit numbers separated by dashes, for example the MGB is 5-13-10. rubber auto oil seals Hyundai.The first figure is the vacuum at which the unit starts to advance, the second is the vacuum at which the unit finishes advancing (both in inches of mercury) while the third figure is the distributor advance in degrees. Thus the vacuum advance on the MGB 25 D distributor:
Starts at 5 inches of mercury
Reaches its maximum advance at 13 inches of mercury
Has a maximum advance of 10 degrees at the distributor (which is 20 deg at the crank of course)
The vacuum advance specs your car should have are given in its workshop manual. This problem is confined almost exclusively to MGB’s with 25D distributors as these had quite a lot if initial mechanical advance compared with A series engines and later MGB’s.rubber auto oil seals Hyundai.
(Note however that replacement distributors are all 45D, some of which are to the same specs as the 25D.)
Any remaining pinking should be followed up as described on the detonation and combustion pages.rubber auto oil seals Hyundai.
rubber auto oil seals Isuzu
This is the advance figure
specified in most manuals. Note that dynamic readings vary with engine
speed, so the specified engine speed is most important. rubber auto oil seals
Isuzu.The problem with using this method is again that most
distributors are high mileage (refer again to my page “Distributor
advance rate adjustments: compensating for high mileage wear”). When
advance mechanisms wear and are not performing to spec, the result is
always correct timing ONLY at the engine speed it was set at – and wrong
everywhere else. However, once you have attended to such discrepancies
it is a very good method.
Strobe timing at full advance
This is the best method for ensuring best power. Generally, the timing on an engine advances steadily as the engine speeds up – but only to a certain point. After this speed is reached no further advance takes place. The engine is then said to have maximum advance.rubber auto oil seals Isuzu.
To set timing by this method:
Find the engine speed at which max advance occurs.
Get a helper to gradually increase throttle and engine speed while you watch the advance with the timing light and see where it is when it stops increasing. This can get rather noisy, as some engines don’t get maximum advance till over 4000 RPM (eg Midget) or even higher (eg late MGB’s). rubber auto oil seals Isuzu.Early MGB’s, on the other hand, get maximum advance at 2300 RPM. (Generally, with wear this maximum will occur sooner than original)
To find what the maximum advance should be, add the max centrifugal advance figure to the static timing figure (the figures to use are those in the manual in both cases). Note: centrifugal advance can sometimes be listed as distributor degrees – if this is the case, double to get crankshaft degrees, as the latter is what you measure with the strobe light. If you can’t find/work out what the maxium advance should be, 30 deg is a good maximum advance figure to use for standard BMC engines.rubber auto oil seals Isuzu.
Alter your timing to achieve this maximum advance figure.
Road test. If the distributor is badly worn the engine will pink. To eliminate this, you will need to sort the distributor (see that page of mine again) or retard it temporarily until doing so – with a consequent loss of power and economy.rubber auto oil seals Isuzu.
Finally, once you have maximum advance set correctly, allow the engine to idle. Take a note of the engine speed and ignition timing – in future you can use this figure for the strobe-at-idle method safe in the knowledge that your engine will get the right maximum advance figure. It will also save the need for a helper and noisy drama each time you set the timing!
Similarly, make a note of the static setting your distributor is now at for use for initial set-up after those occasions when the distributor has been removed such as to fit new points or an engine rebuild.rubber auto oil seals Isuzu.
Strobe timing at full advance
This is the best method for ensuring best power. Generally, the timing on an engine advances steadily as the engine speeds up – but only to a certain point. After this speed is reached no further advance takes place. The engine is then said to have maximum advance.rubber auto oil seals Isuzu.
To set timing by this method:
Find the engine speed at which max advance occurs.
Get a helper to gradually increase throttle and engine speed while you watch the advance with the timing light and see where it is when it stops increasing. This can get rather noisy, as some engines don’t get maximum advance till over 4000 RPM (eg Midget) or even higher (eg late MGB’s). rubber auto oil seals Isuzu.Early MGB’s, on the other hand, get maximum advance at 2300 RPM. (Generally, with wear this maximum will occur sooner than original)
To find what the maximum advance should be, add the max centrifugal advance figure to the static timing figure (the figures to use are those in the manual in both cases). Note: centrifugal advance can sometimes be listed as distributor degrees – if this is the case, double to get crankshaft degrees, as the latter is what you measure with the strobe light. If you can’t find/work out what the maxium advance should be, 30 deg is a good maximum advance figure to use for standard BMC engines.rubber auto oil seals Isuzu.
Alter your timing to achieve this maximum advance figure.
Road test. If the distributor is badly worn the engine will pink. To eliminate this, you will need to sort the distributor (see that page of mine again) or retard it temporarily until doing so – with a consequent loss of power and economy.rubber auto oil seals Isuzu.
Finally, once you have maximum advance set correctly, allow the engine to idle. Take a note of the engine speed and ignition timing – in future you can use this figure for the strobe-at-idle method safe in the knowledge that your engine will get the right maximum advance figure. It will also save the need for a helper and noisy drama each time you set the timing!
Similarly, make a note of the static setting your distributor is now at for use for initial set-up after those occasions when the distributor has been removed such as to fit new points or an engine rebuild.rubber auto oil seals Isuzu.
rubber auto oil seals Jeep
Obviously, with the electronic set up you can’t use methods which detect when the points open. rubber auto oil seals
Jeep.The way to go about static timing under these circumstances is:
Mark the current distributor position, marking both distributor to clamp
and clamp to block. This will allow you to reference whether the timing
was out, and if so by how much. On the Lucas distributors used for
XPAG, A,B and C series engines, 1mm at the distributor base is 6 deg on
the crank so make sure the marks are clear!
Set the crankshaft to the required static timing point with the rotor pointing towards no 1 plug lead
Refit the distributor cap.rubber auto oil seals Jeep.
Either attach your strobe light to no 1 plug lead, or (if you don’t have a light) remove no 1 plug lead and fit a spare spark plug to it (with the body of the plug suitably grounded to the engine)
Find the approximate position for the distributor by rotating the whole distributor fairly rapidly clockwise (i.e. opposite to the way to the rotor turns) until a spark appears (be it at the light or at the spare plug). You may have to rotate the distributor anticlockwise 20 or 30 deg first before doing so in order to ensure the timed position is covered on the clockwise sweep.rubber auto oil seals Jeep.
Having noted the approximate position, refine the process by using a smaller angle of sweep centred on the approximate position and moving the distributor as slowly as it is possible to do yet still get a spark.
Tighten the distributor clamp.rubber auto oil seals Jeep.
This process may end up with a degree or two of extra advance. In engines with timing marks visible from the top, I would then check by rotating the crank and seeing what the pointers read when the spark appeared. However, this is a luxury for engines which still have the timing marks underneath! In any event, the right maximum advance usually results in more advance at static on a worn distributor.rubber auto oil seals Jeep.
Set the crankshaft to the required static timing point with the rotor pointing towards no 1 plug lead
Refit the distributor cap.rubber auto oil seals Jeep.
Either attach your strobe light to no 1 plug lead, or (if you don’t have a light) remove no 1 plug lead and fit a spare spark plug to it (with the body of the plug suitably grounded to the engine)
Find the approximate position for the distributor by rotating the whole distributor fairly rapidly clockwise (i.e. opposite to the way to the rotor turns) until a spark appears (be it at the light or at the spare plug). You may have to rotate the distributor anticlockwise 20 or 30 deg first before doing so in order to ensure the timed position is covered on the clockwise sweep.rubber auto oil seals Jeep.
Having noted the approximate position, refine the process by using a smaller angle of sweep centred on the approximate position and moving the distributor as slowly as it is possible to do yet still get a spark.
Tighten the distributor clamp.rubber auto oil seals Jeep.
This process may end up with a degree or two of extra advance. In engines with timing marks visible from the top, I would then check by rotating the crank and seeing what the pointers read when the spark appeared. However, this is a luxury for engines which still have the timing marks underneath! In any event, the right maximum advance usually results in more advance at static on a worn distributor.rubber auto oil seals Jeep.
rubber auto oil seals Land Rover
All pre-electronic MG engines
are easy to tune and hold no great mysteries, so are easy for owners
who want to do their own maintenance to tackle if they go about it
methodically and in the right sequence.rubber auto oil seals Land Rover.
Generally, if you give your car a thorough tune-up when you buy it, and then tune your car at regular intervals thereafter you will find that you need only to sort the ignition (replace spark plugs, points, condenser and set the ignition timing) and then check the carburettor settings (which usually don’t change by much if at all).
The following comments provide an overview to tuning, with more detailed comments on various aspects covered on other pages.rubber auto oil seals Land Rover.
The vital golden rules:
If you have a problem, do one thing at a time – that way you get to understand what has happened, and more importantly can undo any step which had a perverse effect.
Do the ignition first. I cannot repeat this enough!
Contrary to popular myth, any problem will NOT usually be with the carburettors! (This rule is also known as “Before touching the carburettors, make sure everything else is right first.”)rubber auto oil seals Land Rover.
The initial thorough tune-up:
By thorough tune-up, I mean that before undertaking the usual checks for ignition and carbs you ensure the following are all in good condition:
Distributor – should advance at the correct rate and should not be excessively sloppy in the bearings or drive. Distributor cap and rotor should be in good order.rubber auto oil seals Land Rover.
The cylinders are holding pressure – no significant leakage in the valves or rings – see compression testing, below.
Carburettors – should not be floppy in the throttle spindles and should not be worn significantly in the jets or jet needles. The needle valves should shut off properly and the float should be at the right position when it does so.
It is impossible to properly tune an engine properly which has faults in any of these areas. If any are present, expect only limited results until they are addressed.rubber auto oil seals Land Rover.
Having checked these items, you then need to also check:
The spark plug leads. If in doubt, replace them.
The tappets are set correctly
There are no air leaks into the intake system. A quick visual check is all that is needed initially. However, remember this as a potential cause of puzzling problems.rubber auto oil seals Land Rover.
Generally, if you give your car a thorough tune-up when you buy it, and then tune your car at regular intervals thereafter you will find that you need only to sort the ignition (replace spark plugs, points, condenser and set the ignition timing) and then check the carburettor settings (which usually don’t change by much if at all).
The following comments provide an overview to tuning, with more detailed comments on various aspects covered on other pages.rubber auto oil seals Land Rover.
The vital golden rules:
If you have a problem, do one thing at a time – that way you get to understand what has happened, and more importantly can undo any step which had a perverse effect.
Do the ignition first. I cannot repeat this enough!
Contrary to popular myth, any problem will NOT usually be with the carburettors! (This rule is also known as “Before touching the carburettors, make sure everything else is right first.”)rubber auto oil seals Land Rover.
The initial thorough tune-up:
By thorough tune-up, I mean that before undertaking the usual checks for ignition and carbs you ensure the following are all in good condition:
Distributor – should advance at the correct rate and should not be excessively sloppy in the bearings or drive. Distributor cap and rotor should be in good order.rubber auto oil seals Land Rover.
The cylinders are holding pressure – no significant leakage in the valves or rings – see compression testing, below.
Carburettors – should not be floppy in the throttle spindles and should not be worn significantly in the jets or jet needles. The needle valves should shut off properly and the float should be at the right position when it does so.
It is impossible to properly tune an engine properly which has faults in any of these areas. If any are present, expect only limited results until they are addressed.rubber auto oil seals Land Rover.
Having checked these items, you then need to also check:
The spark plug leads. If in doubt, replace them.
The tappets are set correctly
There are no air leaks into the intake system. A quick visual check is all that is needed initially. However, remember this as a potential cause of puzzling problems.rubber auto oil seals Land Rover.
rubber auto oil seals Kia
The advance mechanisms are covered on other pages on this site.rubber auto oil seals
Kia.Sloppiness in the distributor or its drive causes the timing to
flutter around, or “scatter”. This effect will be readily seen if you
uses a strobe light to look at the timing marks on the crank pulley. The
mark should, ideally, be very steady rather than be jumping about.
In reality, with mechanical distributors some movement usually occurs other than if everything is freshly renewed. A couple of degrees is not unusual and while not ideal is still acceptable. Any timing scatter of more than 5 degrees should be followed up. I have seen up to 20 deg in bad cases!rubber auto oil seals Kia.
Unfortunately, remedies for timing scatter are not cheap or simple, and come down to either a full distributor overhaul (or new distributor) and/or a new camshaft & distributor drive spindle. However, if scatter is bad you will be well rewarded with both power and economy if it is fixed.rubber auto oil seals Kia.
The most common cause of timing scatter in B series engines is wear in the gears which drive the distributor, especially the one on the camshaft since the oil pump is also driven by this.rubber auto oil seals Kia. (A series suffer from this too, but not anywhere near as frequently as the oil pump drive is elsewhere.) For this reason, always check this potential source of scatter before assuming it is the distributor bearings etc worn. To check without removing the camshaft, remove the distributor and see if there is significant backlash in the drive spindle. (Note: backlash can also be caused by the use of a gasket between the distributor mounting fitting and the block, as it allows the spindle to float axially.)rubber auto oil seals Kia.
In reality, with mechanical distributors some movement usually occurs other than if everything is freshly renewed. A couple of degrees is not unusual and while not ideal is still acceptable. Any timing scatter of more than 5 degrees should be followed up. I have seen up to 20 deg in bad cases!rubber auto oil seals Kia.
Unfortunately, remedies for timing scatter are not cheap or simple, and come down to either a full distributor overhaul (or new distributor) and/or a new camshaft & distributor drive spindle. However, if scatter is bad you will be well rewarded with both power and economy if it is fixed.rubber auto oil seals Kia.
The most common cause of timing scatter in B series engines is wear in the gears which drive the distributor, especially the one on the camshaft since the oil pump is also driven by this.rubber auto oil seals Kia. (A series suffer from this too, but not anywhere near as frequently as the oil pump drive is elsewhere.) For this reason, always check this potential source of scatter before assuming it is the distributor bearings etc worn. To check without removing the camshaft, remove the distributor and see if there is significant backlash in the drive spindle. (Note: backlash can also be caused by the use of a gasket between the distributor mounting fitting and the block, as it allows the spindle to float axially.)rubber auto oil seals Kia.
rubber auto oil seals Lexus
If you haven’t encountered
this term before, in this context it refers to measuring the maximum
pressure in the cylinder while the engine is cranking over on the
starter (with the ignition disabled so the car doesn’t start).rubber auto oil seals Lexus.
Check the compressions if:
it is a new (to you) car – if this wasn’t already done prior to purchase
the car has been unused for some time (months, not weeks) as this can cause rusting on the valve seats and consequent lack of sealing
it is some time since you have done one and there is an unusual or elusive problem.rubber auto oil seals Lexus.
Compression testers are relatively cheap (cheaper to buy a gauge than to drive in and pay someone to do the job). Their instructions, or workshop manuals, outline how to use and interpret them. The only comments I will add are:
if you can’t find the correct cranking compression pressures listed for your car, work on 20 times the compression ratio as the figure for a good healthy engine. (For example, 8.8:1 should give about 20 x 8.8 = 176 psi on the compression gauge).
in the absence of any data from the manual, the best indication of condition is that the compressions between different cylinders don’t vary by more than 10 psi.rubber auto oil seals Lexus.
the actual compression readings will vary from those in the manual if the engine is modified.
A simple approximate compression check is to crank the engine over with the plugs in but ignition disconnected, and listen to the beat of the engine. It should be even. To hear what very “uneven” sounds like, remove a spark plug and crank it again (listen to the beat, not the whoosh of air in and out of the plughole).rubber auto oil seals Lexus.
Air leaks
As noted above, air leaks in the inlet tract can be the source of an elusive problem. Some sources are:
The gasket between manifold and head. In particular, the A series manifold gasket is very thin above and below the inlet ports and fails at this point relatively easily.rubber auto oil seals Lexus.
Cracks in the heat shield which extend into the join between carb and manifold
Faulty brake booster (if fitted). To eliminate this as a source, disconnect the vacuum hose from the manifold to the booster and plug it off.
Faulty PCV valve on mid-late 60’s B’s and Midgets. This can be accompanied by excessive oil consumption.
Carburettors or manifold loose. Unusual, but yes, it can happen!rubber auto oil seals Lexus.
Check the compressions if:
it is a new (to you) car – if this wasn’t already done prior to purchase
the car has been unused for some time (months, not weeks) as this can cause rusting on the valve seats and consequent lack of sealing
it is some time since you have done one and there is an unusual or elusive problem.rubber auto oil seals Lexus.
Compression testers are relatively cheap (cheaper to buy a gauge than to drive in and pay someone to do the job). Their instructions, or workshop manuals, outline how to use and interpret them. The only comments I will add are:
if you can’t find the correct cranking compression pressures listed for your car, work on 20 times the compression ratio as the figure for a good healthy engine. (For example, 8.8:1 should give about 20 x 8.8 = 176 psi on the compression gauge).
in the absence of any data from the manual, the best indication of condition is that the compressions between different cylinders don’t vary by more than 10 psi.rubber auto oil seals Lexus.
the actual compression readings will vary from those in the manual if the engine is modified.
A simple approximate compression check is to crank the engine over with the plugs in but ignition disconnected, and listen to the beat of the engine. It should be even. To hear what very “uneven” sounds like, remove a spark plug and crank it again (listen to the beat, not the whoosh of air in and out of the plughole).rubber auto oil seals Lexus.
Air leaks
As noted above, air leaks in the inlet tract can be the source of an elusive problem. Some sources are:
The gasket between manifold and head. In particular, the A series manifold gasket is very thin above and below the inlet ports and fails at this point relatively easily.rubber auto oil seals Lexus.
Cracks in the heat shield which extend into the join between carb and manifold
Faulty brake booster (if fitted). To eliminate this as a source, disconnect the vacuum hose from the manifold to the booster and plug it off.
Faulty PCV valve on mid-late 60’s B’s and Midgets. This can be accompanied by excessive oil consumption.
Carburettors or manifold loose. Unusual, but yes, it can happen!rubber auto oil seals Lexus.
rubber auto oil seals Mazda
If you have a problem with.rubber auto oil seals Mazda.
carburettors touching/denting the bonnet,or
engine mounts breaking under competition use
then read on …
On our Midgets we have put a restraint on the engine mount which allows for the normal range of engine vibration but prevents anything excessive. The restraint has the happy side effect of limiting carb travel upwards over bumps, though it was done mainly because we got tired of breaking engine mounts during autotest reverse to forward flick turns (aka J turns, but done properly it’s a straight line not a J) when the big clutch dump after getting first gear coincides with and engine mount already suffering from engine inertial loads as the car flicks round.rubber auto oil seals Mazda.
The restraint is simply a bit of flat plate bolted to the rear of the engine mount bracket, with a 1/2″ hole at the top. Through the hole protrudes a 5/16″ bolt which is secured firmly to the engine front plate. If the bolt is aligned with the centre of the 1/2″ hole then engine movement of up to 3/32″ (2.5mm if you insist) can take place without restraint. Anything more than that and it’s held back.rubber auto oil seals Mazda.
It’s been 100% successful, no contact in normal use, no more broken engine mounts or panel beater’s bills for straightening a carb-contact nipple out of the bonnet.
I haven’t needed it for any of the other cars, but the principle could easily be applied to other models provided suitable attachment points can be found.rubber auto oil seals Mazda.
carburettors touching/denting the bonnet,or
engine mounts breaking under competition use
then read on …
On our Midgets we have put a restraint on the engine mount which allows for the normal range of engine vibration but prevents anything excessive. The restraint has the happy side effect of limiting carb travel upwards over bumps, though it was done mainly because we got tired of breaking engine mounts during autotest reverse to forward flick turns (aka J turns, but done properly it’s a straight line not a J) when the big clutch dump after getting first gear coincides with and engine mount already suffering from engine inertial loads as the car flicks round.rubber auto oil seals Mazda.
The restraint is simply a bit of flat plate bolted to the rear of the engine mount bracket, with a 1/2″ hole at the top. Through the hole protrudes a 5/16″ bolt which is secured firmly to the engine front plate. If the bolt is aligned with the centre of the 1/2″ hole then engine movement of up to 3/32″ (2.5mm if you insist) can take place without restraint. Anything more than that and it’s held back.rubber auto oil seals Mazda.
It’s been 100% successful, no contact in normal use, no more broken engine mounts or panel beater’s bills for straightening a carb-contact nipple out of the bonnet.
I haven’t needed it for any of the other cars, but the principle could easily be applied to other models provided suitable attachment points can be found.rubber auto oil seals Mazda.
rubber auto oil seals MG
If your engine won’t start
easily when hot, and has good fuel delivery and good spark, it may be
because heat soak is making the fuel expand and rise enough to dribble
out the jet and flood the engine a bit. Although we haven’t struck it
with any of the Midgets, I have had this problem with my MGB. rubber auto oil seals
MG.In that case, it was so bad that between 30 seconds and 20 minutes
after switch-off it would not start with the starter regardless of
throttle position and had to be pushed. Every time! (So parking was
always on a handy hill wherever possible!) Outside of this time it
always started instantly.
In this case it was exacerbated by a combination of big bore engine, very high compression ratio and mild street cam, together putting a lot of load on the starter – and so dropping the battery voltage significantly.rubber auto oil seals MG.
The solution was multipronged:
Dropped the float level a little lower than spec to reduce the amount of flooding. (Having made this change I had to check that it didn’t it lean out under power of course)
Fitted a ballast resistor & ballasted coil so the coil now sees its full operating voltage when the starter is cranking.rubber auto oil seals MG.
Fitted a geared starter to reduce the current drain and therefore system voltage drop.
This completely solved the problem. The engine still floods a little, but with the starter spinning the engine better and the system voltage staying higher and so allowing a fatter spark at the plugs the engine now fires after half a dozen revolutions at worst – usually it’s instant.rubber auto oil seals MG.
There are other causes of hot start difficulty, to check whether the above is relevant to any difficulty you might be experiencing I would suggest that next time it happens you whip off the dashpot & piston from one of the carbs & see if any fuel is dribbling from the jet or (if not) if the fuel level in the jet is at the top and about to overflow. This should confirm or otherwise whether your car is affected in the same way.rubber auto oil seals MG.
If it is, before spending any money try the usual response to flooding of full throttle while cranking on the starter – if that overcomes it it’s a cheaper fix than what I had to do! And check the float level in the carbs – it may be just that it is higher than it should be.rubber auto oil seals MG.
In this case it was exacerbated by a combination of big bore engine, very high compression ratio and mild street cam, together putting a lot of load on the starter – and so dropping the battery voltage significantly.rubber auto oil seals MG.
The solution was multipronged:
Dropped the float level a little lower than spec to reduce the amount of flooding. (Having made this change I had to check that it didn’t it lean out under power of course)
Fitted a ballast resistor & ballasted coil so the coil now sees its full operating voltage when the starter is cranking.rubber auto oil seals MG.
Fitted a geared starter to reduce the current drain and therefore system voltage drop.
This completely solved the problem. The engine still floods a little, but with the starter spinning the engine better and the system voltage staying higher and so allowing a fatter spark at the plugs the engine now fires after half a dozen revolutions at worst – usually it’s instant.rubber auto oil seals MG.
There are other causes of hot start difficulty, to check whether the above is relevant to any difficulty you might be experiencing I would suggest that next time it happens you whip off the dashpot & piston from one of the carbs & see if any fuel is dribbling from the jet or (if not) if the fuel level in the jet is at the top and about to overflow. This should confirm or otherwise whether your car is affected in the same way.rubber auto oil seals MG.
If it is, before spending any money try the usual response to flooding of full throttle while cranking on the starter – if that overcomes it it’s a cheaper fix than what I had to do! And check the float level in the carbs – it may be just that it is higher than it should be.rubber auto oil seals MG.
rubber auto oil seals Mini
If your engine has been running fine and suddenly dies and will not fire at all while cranking on the starter, check:rubber auto oil seals Mini.
Fuel – assuming you have some in the tank!
Remove a fuel line from one of the carbs
With the fuel hose suitably directed to avoid anything hot, turn on the key and see if the pump is working
Ignition –
Check for a spark at the points. If there is not, check the condition and setting of the points. rubber auto oil seals Mini.If that is OK, then –
Check wiring to the coil and distributor for breaks – as insulation ages it can get brittle, crack and precipitate this. (Especially if the insulation has been subjected to oil)
If there is a spark at the points, check the rotor arm. This is perhaps the most common cause of the engine suddenly going dead. A hairline crack in the rotor arm will gather dirt and allow a short circuit to its spindle. (refer photo) Even new rotor arms die occasionally! A simple diagnosis for rotor arm failure is that there will be a spark from the HT lead from the coil to the cap, but no spark at the spark plug leads. (Though this would also be the case if the distributor cap cracks around the centre HT socket)rubber auto oil seals Mini.
Fuel – assuming you have some in the tank!
Remove a fuel line from one of the carbs
With the fuel hose suitably directed to avoid anything hot, turn on the key and see if the pump is working
Ignition –
Check for a spark at the points. If there is not, check the condition and setting of the points. rubber auto oil seals Mini.If that is OK, then –
Check wiring to the coil and distributor for breaks – as insulation ages it can get brittle, crack and precipitate this. (Especially if the insulation has been subjected to oil)
If there is a spark at the points, check the rotor arm. This is perhaps the most common cause of the engine suddenly going dead. A hairline crack in the rotor arm will gather dirt and allow a short circuit to its spindle. (refer photo) Even new rotor arms die occasionally! A simple diagnosis for rotor arm failure is that there will be a spark from the HT lead from the coil to the cap, but no spark at the spark plug leads. (Though this would also be the case if the distributor cap cracks around the centre HT socket)rubber auto oil seals Mini.
rubber auto oil seals Mitsubishi
Both A series (except the
1275) and B series engines had cover plates on the side of the block
providing easy access to the cam followers. rubber auto oil seals
Mitsubishi. On the 1275 (except the early Cooper S blocks) the access
holes were omitted in order to increase block rigidity, meaning the only
way to remove the camshaft is with the engine upside down.
There are two different gaskets for these pushrod covers: 12A1139, the original cork gasket, and 12A1175, a synthetic rubber gasket. A series, MGA and early MGB engines had two of the 12A1139 gaskets, while the later B series had 1 of each.rubber auto oil seals Mitsubishi.
The obvious difference in the material between to two gaskets is purely secondary to their principal differences, which are their are different dimensions. The rubber one is about 1/4″ smaller each way and much thicker. It is made to fit into a recess in a modified rear pushrod cover. Presumably a redesign to improve sealing. For this reason the two are NOT interchangeable.rubber auto oil seals Mitsubishi.
This was introduced at about the time a breather cannister was incorporated into the front pushrod cover cover. The breather structure necessitated the retention of the original sized cork gasket, hence one of each – they aren’t interchangeable (unless an oil leak is wanted!).
All this took place at about the same time as the 1275 with the filled in side chest was introduced. Presumably this is why we haven’t seen the modified A series version, or it could be a classic bit of inconsistency!rubber auto oil seals Mitsubishi.
Don’t mix them up!
Some people elect to fit two rubber gaskets in the mistaken belief that the material is better, but the ruberised cork that 12A1139 is now made of is just as efficient at sealing as 100% synthetic rubber. However size IS important because the rubber gasket coverage over the front pushrod cover is reduced to almost nothing in one corner, so not good enough to give a reliable seal.rubber auto oil seals Mitsubishi.
A simple guide to the use of these gaskets is that if it doesn’t fit properly you probably have the wrong one!
It’s interesting that a number of parts listings scramble the two. It gives the feeling that those responsible for the listing have never actually tried to fit one!
Seal for the centre bolt
One definite advantage of the redesign was the use of a cup washer (12A1177) and O-ring (12A1176) to seal the bolt in the centre. This is a worthwhile (and cheap) retro-fit for those cars still fitted with flat & fibre washers.rubber auto oil seals Mitsubishi.
There are two different gaskets for these pushrod covers: 12A1139, the original cork gasket, and 12A1175, a synthetic rubber gasket. A series, MGA and early MGB engines had two of the 12A1139 gaskets, while the later B series had 1 of each.rubber auto oil seals Mitsubishi.
The obvious difference in the material between to two gaskets is purely secondary to their principal differences, which are their are different dimensions. The rubber one is about 1/4″ smaller each way and much thicker. It is made to fit into a recess in a modified rear pushrod cover. Presumably a redesign to improve sealing. For this reason the two are NOT interchangeable.rubber auto oil seals Mitsubishi.
This was introduced at about the time a breather cannister was incorporated into the front pushrod cover cover. The breather structure necessitated the retention of the original sized cork gasket, hence one of each – they aren’t interchangeable (unless an oil leak is wanted!).
All this took place at about the same time as the 1275 with the filled in side chest was introduced. Presumably this is why we haven’t seen the modified A series version, or it could be a classic bit of inconsistency!rubber auto oil seals Mitsubishi.
Don’t mix them up!
Some people elect to fit two rubber gaskets in the mistaken belief that the material is better, but the ruberised cork that 12A1139 is now made of is just as efficient at sealing as 100% synthetic rubber. However size IS important because the rubber gasket coverage over the front pushrod cover is reduced to almost nothing in one corner, so not good enough to give a reliable seal.rubber auto oil seals Mitsubishi.
A simple guide to the use of these gaskets is that if it doesn’t fit properly you probably have the wrong one!
It’s interesting that a number of parts listings scramble the two. It gives the feeling that those responsible for the listing have never actually tried to fit one!
Seal for the centre bolt
One definite advantage of the redesign was the use of a cup washer (12A1177) and O-ring (12A1176) to seal the bolt in the centre. This is a worthwhile (and cheap) retro-fit for those cars still fitted with flat & fibre washers.rubber auto oil seals Mitsubishi.
rubber auto oil seals Nissan
Excessive tappet noise is an
indication that something needs attending to. Even the B series
engine, renowned for tappet noise, is quite quiet in the valve gear with
newly reground cam and followers.rubber auto oil seals Nissan.
Initially you should check the tappet adjustment (you probably already have). If you have a B series engine, see below regarding the clearance to use. See also the page on valve clearances.
If that doesn’t reduce the noise, you need to check for worn valve gear. This will have been caused by previous owners not keeping the tappet adjustment correct – it’s an infrequently needed job, but in addition to the specified intervals it should be attended to immediately if tappets get noisy or the valve gear will hammer away to serious wear.rubber auto oil seals Nissan.
Places where wear occurs initially are in the rocker shaft and bushes, cam followers. If worn & pitted followers are not replaced soon enough, they grind away at the cam lobe. This can happen to such an extent that the valve effectively stops opening!rubber auto oil seals Nissan.
If you have access to a dial gauge, the simplest way to check for cam lobe wear is to measure the lift at each pushrod (having temporarily removed tappet clearance) and compare it with the specified lift for the cam profile. For the standard 1275 exhaust lobes and the standard MGA & B camshaft this should be 0.268″ (being the listed cam lift plus the checking clearance of .016″)rubber auto oil seals Nissan.
I have preferred to run the B series tappet clearance at 0.013″ (cold), as the 0.015″ (cold) specified in the manual results in the clearance being taken up right at the end of the cam lobe’s opening ramp. At 15 thou, any wear then results in the clearance being taken up at higher velocity (with attendant higher wear rates) whereas at 13 thou the clearance can increase to 15 thou and still be on the ramp. This is about how much it will wear if the tappet clearance is checked at the intervals specified in the manual. In my experience, the reduced clearance has made negligible difference to the engine’s performance and idle, and even in cars driven hard it has not had any effect on valve life.rubber auto oil seals Nissan.
Interestingly, further evidence that .013” is a better clearance to use in the B series is provided if we look at the A series. The latter tappet clearance is specified at .012”. The BMC cams all used the same opening ramp detail so a direct comparison with the B series is relevant if the rocker ratio is allowed for. Doing this, we find that 12 thou on the A series rocker ratio would be the same point on the cam as 13.4 thou on the B series rocker ratio.rubber auto oil seals Nissan.
Initially you should check the tappet adjustment (you probably already have). If you have a B series engine, see below regarding the clearance to use. See also the page on valve clearances.
If that doesn’t reduce the noise, you need to check for worn valve gear. This will have been caused by previous owners not keeping the tappet adjustment correct – it’s an infrequently needed job, but in addition to the specified intervals it should be attended to immediately if tappets get noisy or the valve gear will hammer away to serious wear.rubber auto oil seals Nissan.
Places where wear occurs initially are in the rocker shaft and bushes, cam followers. If worn & pitted followers are not replaced soon enough, they grind away at the cam lobe. This can happen to such an extent that the valve effectively stops opening!rubber auto oil seals Nissan.
If you have access to a dial gauge, the simplest way to check for cam lobe wear is to measure the lift at each pushrod (having temporarily removed tappet clearance) and compare it with the specified lift for the cam profile. For the standard 1275 exhaust lobes and the standard MGA & B camshaft this should be 0.268″ (being the listed cam lift plus the checking clearance of .016″)rubber auto oil seals Nissan.
I have preferred to run the B series tappet clearance at 0.013″ (cold), as the 0.015″ (cold) specified in the manual results in the clearance being taken up right at the end of the cam lobe’s opening ramp. At 15 thou, any wear then results in the clearance being taken up at higher velocity (with attendant higher wear rates) whereas at 13 thou the clearance can increase to 15 thou and still be on the ramp. This is about how much it will wear if the tappet clearance is checked at the intervals specified in the manual. In my experience, the reduced clearance has made negligible difference to the engine’s performance and idle, and even in cars driven hard it has not had any effect on valve life.rubber auto oil seals Nissan.
Interestingly, further evidence that .013” is a better clearance to use in the B series is provided if we look at the A series. The latter tappet clearance is specified at .012”. The BMC cams all used the same opening ramp detail so a direct comparison with the B series is relevant if the rocker ratio is allowed for. Doing this, we find that 12 thou on the A series rocker ratio would be the same point on the cam as 13.4 thou on the B series rocker ratio.rubber auto oil seals Nissan.
rubber auto oil seals Opel
It is often difficult to
determine whether valve seat inserts have been fitted before, when
viewed only from the chamber, – the original machining usually left a
pattern which is not to dissimilar to how it looks with seat inserts.rubber auto oil seals Opel.
The usual give-away as to whether inserts have been fitted is to feel round the short radius with your finger. If an insert has been fitted to an unmodified head there is invariably a bit of a ledge in the short radius where the seat finishes. (short radius – the tight side of the 90 deg bend between valve seat and port. Alternatively described as where the bottom [when the head is on the engine] of the port turns the corner to the valve seat.)
Inserts, if fitted, may be hardened but could also be of the cast iron variety used in the past to effect repairs or reclaim worn seats. The simplest way to confirm is to use a small file on the inside of the insert (NOT where it forms the valve seat) to see whether it marks/cuts into it easily or not.rubber auto oil seals Opel.
I often get asked what is the best way to deal with this.
The options are:
Additives added to the tank when you top-up with fuel
In-line tin-based canisters
Stainless valve seat inserts.
Stainless valve seats
My personal preference is to fit stainless valve seats as they are the reason modern engines run perfectly happy for ever on unleaded fuel. I would recommend that if you have the head off for some other reason that you get them fitted then, as it is a relatively inexpensive job – the last one I had done was $200. However, I wouldn’t suggest you pull the head off specially to do this job unless you use the engine in the higher speed range (see below).rubber auto oil seals Opel.
An additional advantage is that hardened inserts greatly increase the reliability and resilience of the head in the event of a burnt exhaust valve. As series heads in particular are prone to cracking when this happens, but if a seat has been fitted it avoids this damage.
If you have a head with oversize valves, refer further down the page for further comment in fitting inserts.
Additives & cannistersrubber auto oil seals Opel.
Add-to-tank additives are generally reasonably effective, and are the officially recommended way to go if the valve seats are not converted.
In-line canisters have caused a lot of debate. Scientific testing has concluded they are of limited merit but many people swear by them.
There is a school of thought which says there is a “lead memory” and that provided the engine has been run on leaded fuel at some stage then it should be fine. I’ve seen no evidence one way or the other on this.
Valve seat recession is not significant at lower engine speeds (under 2500 RPM) so if engines are always driven at about this speed you could easily get misleading anecdotal evidence about the merits of various additives or about whether they are needed at all.rubber auto oil seals Opel.
Above 4000 RPM, recession becomes much more marked. The in-tank additives reduce it under these conditions but it is still there. That’s why I went for stainless seats, as I do quite a bit of competing.
If you do decide to try omitting the additive altogether, all you need to do is monitor the valve clearances, (only exhaust, inlets are no problem) probably after 1000 miles, then if nothing significant every 2000 miles.
If the seats do start to erode, then either revert to the additive or have stainless seats fitted for a permanent cure. If the seats erode badly, stainless inserts will recover the situation.
If you have oversize valves fitted:rubber auto oil seals Opel.
Many head modifiers and reconditioners are reluctant to fit inserts to heads fitted with oversize valves, in case the pressure of the insert results in a crack across the inlet seats between the valves as the strength there is reduced by the valves being so close together. However, my own experience has shown it is possible to fit seats in these situations & retain complete reliability in this respect.
My MGB big-valve head has the valves only 30 thou apart and has inserts fitted. What we have done to get around the cracking is to insert both inlet and exhaust, with the exhaust insert cut into the outside of the inlet insert a bit. This means that the inserts push on each other rather than just one exerting pressure on the thin bit between the ports. It has been a very successful arrangement, allowing the throat configuration and diameter under both valves to be at their optimum.rubber auto oil seals Opel.
We adopted this arrangement after inserting just the exhausts caused one of the inlet seats to crack within a couple of years and I was reluctant to scrap a head that was the best flowing B head we’d tested. Fitting the inserts to the inlet did not affect the flow once they were blended in.
That was in the 1980’s, so I guess you could say it’s been successful.
We didn’t go unleaded in New Zealand until the ’90’s, the reason for the inserts were pocketed exhaust valve seats. At the time, most inserts being fitted were cast iron but the machine shop suggested new-fangled stainless ones (which were on the market here at the time for CNG/LPG conversions which abounded at the time) as they were stronger and so could be machined much thinner, allowing the throat size I wanted while still just avoiding the inlet seat.rubber auto oil seals Opel.
The usual give-away as to whether inserts have been fitted is to feel round the short radius with your finger. If an insert has been fitted to an unmodified head there is invariably a bit of a ledge in the short radius where the seat finishes. (short radius – the tight side of the 90 deg bend between valve seat and port. Alternatively described as where the bottom [when the head is on the engine] of the port turns the corner to the valve seat.)
Inserts, if fitted, may be hardened but could also be of the cast iron variety used in the past to effect repairs or reclaim worn seats. The simplest way to confirm is to use a small file on the inside of the insert (NOT where it forms the valve seat) to see whether it marks/cuts into it easily or not.rubber auto oil seals Opel.
I often get asked what is the best way to deal with this.
The options are:
Additives added to the tank when you top-up with fuel
In-line tin-based canisters
Stainless valve seat inserts.
Stainless valve seats
My personal preference is to fit stainless valve seats as they are the reason modern engines run perfectly happy for ever on unleaded fuel. I would recommend that if you have the head off for some other reason that you get them fitted then, as it is a relatively inexpensive job – the last one I had done was $200. However, I wouldn’t suggest you pull the head off specially to do this job unless you use the engine in the higher speed range (see below).rubber auto oil seals Opel.
An additional advantage is that hardened inserts greatly increase the reliability and resilience of the head in the event of a burnt exhaust valve. As series heads in particular are prone to cracking when this happens, but if a seat has been fitted it avoids this damage.
If you have a head with oversize valves, refer further down the page for further comment in fitting inserts.
Additives & cannistersrubber auto oil seals Opel.
Add-to-tank additives are generally reasonably effective, and are the officially recommended way to go if the valve seats are not converted.
In-line canisters have caused a lot of debate. Scientific testing has concluded they are of limited merit but many people swear by them.
There is a school of thought which says there is a “lead memory” and that provided the engine has been run on leaded fuel at some stage then it should be fine. I’ve seen no evidence one way or the other on this.
Valve seat recession is not significant at lower engine speeds (under 2500 RPM) so if engines are always driven at about this speed you could easily get misleading anecdotal evidence about the merits of various additives or about whether they are needed at all.rubber auto oil seals Opel.
Above 4000 RPM, recession becomes much more marked. The in-tank additives reduce it under these conditions but it is still there. That’s why I went for stainless seats, as I do quite a bit of competing.
If you do decide to try omitting the additive altogether, all you need to do is monitor the valve clearances, (only exhaust, inlets are no problem) probably after 1000 miles, then if nothing significant every 2000 miles.
If the seats do start to erode, then either revert to the additive or have stainless seats fitted for a permanent cure. If the seats erode badly, stainless inserts will recover the situation.
If you have oversize valves fitted:rubber auto oil seals Opel.
Many head modifiers and reconditioners are reluctant to fit inserts to heads fitted with oversize valves, in case the pressure of the insert results in a crack across the inlet seats between the valves as the strength there is reduced by the valves being so close together. However, my own experience has shown it is possible to fit seats in these situations & retain complete reliability in this respect.
My MGB big-valve head has the valves only 30 thou apart and has inserts fitted. What we have done to get around the cracking is to insert both inlet and exhaust, with the exhaust insert cut into the outside of the inlet insert a bit. This means that the inserts push on each other rather than just one exerting pressure on the thin bit between the ports. It has been a very successful arrangement, allowing the throat configuration and diameter under both valves to be at their optimum.rubber auto oil seals Opel.
We adopted this arrangement after inserting just the exhausts caused one of the inlet seats to crack within a couple of years and I was reluctant to scrap a head that was the best flowing B head we’d tested. Fitting the inserts to the inlet did not affect the flow once they were blended in.
That was in the 1980’s, so I guess you could say it’s been successful.
We didn’t go unleaded in New Zealand until the ’90’s, the reason for the inserts were pocketed exhaust valve seats. At the time, most inserts being fitted were cast iron but the machine shop suggested new-fangled stainless ones (which were on the market here at the time for CNG/LPG conversions which abounded at the time) as they were stronger and so could be machined much thinner, allowing the throat size I wanted while still just avoiding the inlet seat.rubber auto oil seals Opel.
rubber auto oil seals Peugeot
An engine freshen-up is a term that means different things to different people.rubber auto oil seals
Peugeot.In the context of the following I have taken it to be replacing
the rings and bearing shells and attending to other items on an
as-required basis. Taking this approach, the following points may be
useful in considering other components:Oil pump or rotor kit – what was
the oil pressure like before stripping the engine? If over 30 psi at
idle (about 700 – 800 RPM) when hot, then the pump should be OK.
Cam followers – the Achilles heel of the B series in particular – is there any sign of pitting? If there is (even slight), replace them as they will wear out the camshaft quickly. I strongly advise against refacing followers, as they are very soft once the hardened skin has been penetrated – furthermore the cost of refacing is only marginally less than new followers.rubber auto oil seals Peugeot.
Camshaft – If pitting in the followers is bad, check the camshaft for wear and get reground if necessary. The lift of each lobe of a standard MGA or MGB cam should be 0.268”. For the Midget the valve lift when set to the running clearance is listed as 0.312”, which equates to 0.250” cam lift after allowing for the rocker ratio. The XPAG engine of T-types are particularly prone to cam lobe wear, To measure cam lift, measure the largest “diameter” of the lobe – from cam peak to the other side – then subtract the base circle diameter (measure at right angles to the first measurement). Accept wear less than 3 thou. Wear will be evident from varying lifts between lobes.rubber auto oil seals Peugeot.
Timing chain and tensioner – renew unless perfect – they are cheap.
Rocker shaft and bushes – look for wear on the shaft under the rockers (slide them to one side, look at the bottom of the shaft.) If the shaft is worn, renew it. Slide the rockers along the shaft to an unworn bush and check for slackness. Renew the bushes if necessary (they will need fitting and reaming to size).rubber auto oil seals Peugeot.
Unleaded conversion – If your head has not been fitted with hardened exhaust seats, I’d strongly recommend doing it now while the head is off. It is relatively inexpensive so the pay-back period due to not having to use additive is not that long. On top of that, there is less hassle and the seats give added protection to the head from cracking in the event of a valve burning out. It pays to renew the exhaust valves when doing this job, they are reasonably priced.rubber auto oil seals Peugeot.
Ring gear – If your car doesn’t have a pre-engage starter, then check the ring gear for wear. Pre-engage starters were introduced in 1968 for the MGB only along with the full synchromesh gearbox. The Midget continued with the inertia starter. (Note that a first registered 1968 car could have been made in 1967 as there is shipping and showroom time to add to the manufacture date)rubber auto oil seals Peugeot.
Cam followers – the Achilles heel of the B series in particular – is there any sign of pitting? If there is (even slight), replace them as they will wear out the camshaft quickly. I strongly advise against refacing followers, as they are very soft once the hardened skin has been penetrated – furthermore the cost of refacing is only marginally less than new followers.rubber auto oil seals Peugeot.
Camshaft – If pitting in the followers is bad, check the camshaft for wear and get reground if necessary. The lift of each lobe of a standard MGA or MGB cam should be 0.268”. For the Midget the valve lift when set to the running clearance is listed as 0.312”, which equates to 0.250” cam lift after allowing for the rocker ratio. The XPAG engine of T-types are particularly prone to cam lobe wear, To measure cam lift, measure the largest “diameter” of the lobe – from cam peak to the other side – then subtract the base circle diameter (measure at right angles to the first measurement). Accept wear less than 3 thou. Wear will be evident from varying lifts between lobes.rubber auto oil seals Peugeot.
Timing chain and tensioner – renew unless perfect – they are cheap.
Rocker shaft and bushes – look for wear on the shaft under the rockers (slide them to one side, look at the bottom of the shaft.) If the shaft is worn, renew it. Slide the rockers along the shaft to an unworn bush and check for slackness. Renew the bushes if necessary (they will need fitting and reaming to size).rubber auto oil seals Peugeot.
Unleaded conversion – If your head has not been fitted with hardened exhaust seats, I’d strongly recommend doing it now while the head is off. It is relatively inexpensive so the pay-back period due to not having to use additive is not that long. On top of that, there is less hassle and the seats give added protection to the head from cracking in the event of a valve burning out. It pays to renew the exhaust valves when doing this job, they are reasonably priced.rubber auto oil seals Peugeot.
Ring gear – If your car doesn’t have a pre-engage starter, then check the ring gear for wear. Pre-engage starters were introduced in 1968 for the MGB only along with the full synchromesh gearbox. The Midget continued with the inertia starter. (Note that a first registered 1968 car could have been made in 1967 as there is shipping and showroom time to add to the manufacture date)rubber auto oil seals Peugeot.
rubber auto oil seals Porsche
There are two faults which show up in the breather systems of Midgets
and MGBs which cause dramatic oil consumption and lots of blue smoke,
even with a reconditioned engine. rubber auto oil seals
Porsche.Quite a number of engines have been unnecessarily reconditioned
because of these faults so if you have a smoky engine, although the
odds are that it does need overhaul, check these out before you dive in
and spend lots of money:
First miracle cure:
The breather pollution control valve on the manifold, where fitted, (approx 1964 to 1969-70 – 18GA, 18GB, 18GD MGB engines, 10CC, 12CC and early 12CE Midget engines) can develop a leak which allows the crank case to be significantly vented to the inlet manifold under high vacuum rather than only under full-ish throttle conditions when the manifold pressure is much closer to atmospheric. The result is that the strong vacuum sucks furiously at the crankcase, scavenging neat oil as well as the intended fumes into the inlet system. Hence oil combustion and blue smoke!rubber auto oil seals Porsche.
The valve is readily identifiable: It is attached to the middle of the inlet manifold and has a flat circular top of about 3” diameter. A hose joins the outlet (points towards the front of the car) to the breather on the side of the block.
To confirm the diagnosis: remove the PCV valve but leave the hose which joined it to the manifold in place. Block this hole off with a suitable bolt or whatever, and road test to see if the problem has gone.
Many an engine has been needlessly overhauled because of failure to check this out!
Replacing the diaphragm, or if necessary the whole valve (depending on the nature of the fault) will fix the problem in 10 minutes.rubber auto oil seals Porsche.
Warning: While it is tempting and much cheaper to simply vent the breather to atmosphere, doing so makes the engine more likely to leak oil – particularly if it is an A series Midget or 3 bearing MGB. The reason for this is that in its operation the breather maintains a small partial vacuum in the crankcase, which works against oil getting pushed out of the seals (or the rear scroll in the case of the 3 brg B & A series). Venting to atmosphere achieves the reverse effect – it maintains a small residual pressure inside the crankcase (it won’t be much, but without any pressure difference at all there would be no outward flow through the breather).
The partial vacuum system is used by all cars now and is one of the reasons modern engines don’t leak oil.
The other miracle cure:
The breather oil separator on the engine can become blocked, in which case simply cleaning it out solves the oil consumption problem.rubber auto oil seals Porsche.
This unit is incorporated in the front pushrod cover on MGB’s, while on 1275 Midgets it is attached to the timing chain cover. (Sorry, the 10CC engine’s arrangement has slipped my memory at the moment but it will be one or the other of these two).
There were two versions of the pushrod cover separator, the early one had a row of small-ish holes along the botom of the inside face while the later one had a much larger hole about 1.5 – 2″ square-ish at the rear end of this face.
It is the small hole version of the pushrod cover separator which is most prone to blocking up.rubber auto oil seals Porsche.
As described by Robert Paterson:
“Well, I’ve found the answer at last! Last week I took off the “side cover with separator” and it was just as you said, with small holes along the bottom. I could blow through it ok, so it was not blocked.
I decided to drill out the holes to a bigger size. When doing this, I found that it was full of very black goo! In fact, it took me three days to remove the goo – 37 years of old thick solid oil.
I fitted it back on the car and off we went with no problems – no more blue smoke! In fact, the motor seems to be a lot better and more alive, if you know what I mean.”
A simple way to address the gunge is to get an engine reconditioner to put in the cleaning tank.rubber auto oil seals Porsche.
First miracle cure:
The breather pollution control valve on the manifold, where fitted, (approx 1964 to 1969-70 – 18GA, 18GB, 18GD MGB engines, 10CC, 12CC and early 12CE Midget engines) can develop a leak which allows the crank case to be significantly vented to the inlet manifold under high vacuum rather than only under full-ish throttle conditions when the manifold pressure is much closer to atmospheric. The result is that the strong vacuum sucks furiously at the crankcase, scavenging neat oil as well as the intended fumes into the inlet system. Hence oil combustion and blue smoke!rubber auto oil seals Porsche.
The valve is readily identifiable: It is attached to the middle of the inlet manifold and has a flat circular top of about 3” diameter. A hose joins the outlet (points towards the front of the car) to the breather on the side of the block.
To confirm the diagnosis: remove the PCV valve but leave the hose which joined it to the manifold in place. Block this hole off with a suitable bolt or whatever, and road test to see if the problem has gone.
Many an engine has been needlessly overhauled because of failure to check this out!
Replacing the diaphragm, or if necessary the whole valve (depending on the nature of the fault) will fix the problem in 10 minutes.rubber auto oil seals Porsche.
Warning: While it is tempting and much cheaper to simply vent the breather to atmosphere, doing so makes the engine more likely to leak oil – particularly if it is an A series Midget or 3 bearing MGB. The reason for this is that in its operation the breather maintains a small partial vacuum in the crankcase, which works against oil getting pushed out of the seals (or the rear scroll in the case of the 3 brg B & A series). Venting to atmosphere achieves the reverse effect – it maintains a small residual pressure inside the crankcase (it won’t be much, but without any pressure difference at all there would be no outward flow through the breather).
The partial vacuum system is used by all cars now and is one of the reasons modern engines don’t leak oil.
The other miracle cure:
The breather oil separator on the engine can become blocked, in which case simply cleaning it out solves the oil consumption problem.rubber auto oil seals Porsche.
This unit is incorporated in the front pushrod cover on MGB’s, while on 1275 Midgets it is attached to the timing chain cover. (Sorry, the 10CC engine’s arrangement has slipped my memory at the moment but it will be one or the other of these two).
There were two versions of the pushrod cover separator, the early one had a row of small-ish holes along the botom of the inside face while the later one had a much larger hole about 1.5 – 2″ square-ish at the rear end of this face.
It is the small hole version of the pushrod cover separator which is most prone to blocking up.rubber auto oil seals Porsche.
As described by Robert Paterson:
“Well, I’ve found the answer at last! Last week I took off the “side cover with separator” and it was just as you said, with small holes along the bottom. I could blow through it ok, so it was not blocked.
I decided to drill out the holes to a bigger size. When doing this, I found that it was full of very black goo! In fact, it took me three days to remove the goo – 37 years of old thick solid oil.
I fitted it back on the car and off we went with no problems – no more blue smoke! In fact, the motor seems to be a lot better and more alive, if you know what I mean.”
A simple way to address the gunge is to get an engine reconditioner to put in the cleaning tank.rubber auto oil seals Porsche.
Thursday, March 19, 2015
rubber auto oil seals Renault
MGA, MGB 3 main bearing, and
MGB 5 main bearing engines all had different water pumps. MGB 5 bearing
engines also had two types of water pump, differing in their length.rubber auto oil seals Renault.
When ordering replacements, it helps to check which pump type you have, since with the passage of time the original pump may have been changed to another type.
To check the pump type:
MGA pump (GWP103) and 3 main bearing MGB pump (GWP115) have a smaller (60.3mm) impeller.rubber auto oil seals Renault.
The earlier 5 bearing pump (GWP114) fitted on enignes 18GB to 18GG had the steel fan with no spacer between fan and the pulley.
The later 5 bearing pumps (GWP130) can be identified by the presence of a spacer approx 20-25mm thick between the pulley & the original 3 bladed steel fan, or by the presence of a 7 bladed plastic fan.rubber auto oil seals Renault.
Other applications:
Obviously, this range of pumps was used on contemporary BMC B series engines. The MGA pump GWP103 also does all B series 1500 and 1622cc engines other than vans/commercials produced in the late ’60’s and ’70’s. These engines had the 5 main gearing type of pump.
5 bearing pumps: GWP114 was used in the BMC 1800 and GWP 130 was used in the Marina 1800.rubber auto oil seals Renault.
When ordering replacements, it helps to check which pump type you have, since with the passage of time the original pump may have been changed to another type.
To check the pump type:
MGA pump (GWP103) and 3 main bearing MGB pump (GWP115) have a smaller (60.3mm) impeller.rubber auto oil seals Renault.
The earlier 5 bearing pump (GWP114) fitted on enignes 18GB to 18GG had the steel fan with no spacer between fan and the pulley.
The later 5 bearing pumps (GWP130) can be identified by the presence of a spacer approx 20-25mm thick between the pulley & the original 3 bladed steel fan, or by the presence of a 7 bladed plastic fan.rubber auto oil seals Renault.
Other applications:
Obviously, this range of pumps was used on contemporary BMC B series engines. The MGA pump GWP103 also does all B series 1500 and 1622cc engines other than vans/commercials produced in the late ’60’s and ’70’s. These engines had the 5 main gearing type of pump.
5 bearing pumps: GWP114 was used in the BMC 1800 and GWP 130 was used in the Marina 1800.rubber auto oil seals Renault.
rubber auto oil seals Skoda
In New Zealand as we don’t
have a salt-induced corrosion problem from the outside as they do in the
UK, so a stainless system hasn’t quite the same imperative here. rubber auto oil seals
Skodarubber auto oil seals Skoda.However, stainless can still be more
economical if you are keeping your car long term, so here are a few
thoughts to guide you as to whether or not to outlay the extra money for
stainless system:Our exhaust systems corrode from the inside outwards,
and that corrosion is primarily from condensation in the system. rubber auto oil seals. So the
coolest parts of the system are most at risk.
Stainless twin front pipes are fairly redundant since (being the front pipes) they run hotter and don’t suffer from condensation as much as the rear of the system does. As a result, they usually last about 10 years or more, whereas the average life for the silencers is 2 – 6 years depending on the frequency of use.rubber auto oil seals Skoda.
Intermittent gentle use of your car is the real killer of mild steel exhausts as more condensation occurs and it sits around merrily eating away at the silencers until the next time the car is used. Mild steel systems used like this can rot out in 18 months. Under these conditions, stainless systems are far more economical in the long run.rubber auto oil seals Skoda.
Thrashing a car prolongs exhaust life (but obviously it’s hard on everything else!) so if you are an incurable lead-foot, a mild steel system will do the job admirably!
This entry was posted in Fuel and Exhaust, MGA-MGB, Midget. Bookmark the permalink.rubber auto oil seals Skoda.
Stainless twin front pipes are fairly redundant since (being the front pipes) they run hotter and don’t suffer from condensation as much as the rear of the system does. As a result, they usually last about 10 years or more, whereas the average life for the silencers is 2 – 6 years depending on the frequency of use.rubber auto oil seals Skoda.
Intermittent gentle use of your car is the real killer of mild steel exhausts as more condensation occurs and it sits around merrily eating away at the silencers until the next time the car is used. Mild steel systems used like this can rot out in 18 months. Under these conditions, stainless systems are far more economical in the long run.rubber auto oil seals Skoda.
Thrashing a car prolongs exhaust life (but obviously it’s hard on everything else!) so if you are an incurable lead-foot, a mild steel system will do the job admirably!
This entry was posted in Fuel and Exhaust, MGA-MGB, Midget. Bookmark the permalink.rubber auto oil seals Skoda.
rubber auto oil seals Skoda
In New Zealand as we don’t
have a salt-induced corrosion problem from the outside as they do in the
UK, so a stainless system hasn’t quite the same imperative here. rubber auto oil seals
Skodarubber auto oil seals Skoda.However, stainless can still be more
economical if you are keeping your car long term, so here are a few
thoughts to guide you as to whether or not to outlay the extra money for
stainless system:Our exhaust systems corrode from the inside outwards,
and that corrosion is primarily from condensation in the system. rubber auto oil seals. So the
coolest parts of the system are most at risk.
Stainless twin front pipes are fairly redundant since (being the front pipes) they run hotter and don’t suffer from condensation as much as the rear of the system does. As a result, they usually last about 10 years or more, whereas the average life for the silencers is 2 – 6 years depending on the frequency of use.rubber auto oil seals Skoda.
Intermittent gentle use of your car is the real killer of mild steel exhausts as more condensation occurs and it sits around merrily eating away at the silencers until the next time the car is used. Mild steel systems used like this can rot out in 18 months. Under these conditions, stainless systems are far more economical in the long run.rubber auto oil seals Skoda.
Thrashing a car prolongs exhaust life (but obviously it’s hard on everything else!) so if you are an incurable lead-foot, a mild steel system will do the job admirably!
This entry was posted in Fuel and Exhaust, MGA-MGB, Midget. Bookmark the permalink.rubber auto oil seals Skoda.
Stainless twin front pipes are fairly redundant since (being the front pipes) they run hotter and don’t suffer from condensation as much as the rear of the system does. As a result, they usually last about 10 years or more, whereas the average life for the silencers is 2 – 6 years depending on the frequency of use.rubber auto oil seals Skoda.
Intermittent gentle use of your car is the real killer of mild steel exhausts as more condensation occurs and it sits around merrily eating away at the silencers until the next time the car is used. Mild steel systems used like this can rot out in 18 months. Under these conditions, stainless systems are far more economical in the long run.rubber auto oil seals Skoda.
Thrashing a car prolongs exhaust life (but obviously it’s hard on everything else!) so if you are an incurable lead-foot, a mild steel system will do the job admirably!
This entry was posted in Fuel and Exhaust, MGA-MGB, Midget. Bookmark the permalink.rubber auto oil seals Skoda.
rubber auto oil seals Subaru
The USA spec fuel cap fitted
to many MGB’s & Midgets was unvented and as a result sometimes there
is a big suck of air when you undo the fuel cap. – to such an extent
that the bottom of the tank on the Midget of ours with such a cap gets
sucked up a couple of inches and there’s a big metallic clang when the
cap is taken off and the tank fills with air! rubber auto oil seals Subaru. The obvious question that then arises is whether this affects the fuel delivery from the pump.
Our experience is that it does occasionally play silly beggars with the fuel flow but not often. It seems that the only time it interrupts fuel supply is when fuel is low and the bottom of the tank is sucked up the pick-up is left high & dry on an island of tank bottom with the fuel around the edges. And the gauge is fooled – reads nearly 1/2 too! We have learned that when the fuel gauge starts to increase it’s a warning of this about to happen!rubber auto oil seals Subaru.
So in summary the non-vented cap doesn’t seem to inhibit fuel delivery when the tank is at negative pressure. And presumably the very large number of cars sold in the USA would attest to that too!
The original SU pump is very reliable for about 12 – 15 years.
Once it starts to falter, overhaul it and it will be good for another 12 – 15 years.rubber auto oil seals.
The SU pump only ever had one problem – that when it did get old and tired and falter, it would respond to a tap (which eventually becomes a hit as it gets worse) and start working again. Thus, people would not get around to overhauling it (just give it another hit), yet mutter about the unreliability (hit it again) of it every time they had to crawl under the car and HIT IT. So was born one of the great urban motoring myths! Of course it was unreliable then – it was worn out! It’s a bit like running tyres worn through to the cords and wondering why you lose the air so often!
FIX IT, DON’T HIT IT!
A new set of points and a new diaphragm (include new valves for a belts & braces approach), all correctly adjusted as per the workshop manual, and it will run happily for another 12 – 15 years. As simple as that!
Finally, (for what it is worth) avoid the electronic SU clones – I get a lot of feedback about them failing.rubber auto oil seals Subaru.
If your pump operates too rapidly, There are only five possible causes:
No petrol in tank, or faulty pick-up
If the system has been opened up – the pump is not yet primed (quite common) This can happen when it is working against air pressure and the air pressure confuses the pump’s valves) To check, disconnect the outlet hose of the pump from the pipe going forwards to the engine and operate the pump until petrol comes out the hose. If air comes out initially, this is likely the problem. Reconnect and the pump should then operate for a while until filling the carbs, after which it should slow to a click every 5 – 10 seconds as per normal.rubber auto oil seals Subaru.
Air weeping into the intake line at a joint (this is possible even though there is no petrol weeping out). Double check all joints for tightness.
Grit under the valve in the pump (sucked through from the tank) Clean out tank.
Faulty valve in the pump. Renew valve.
Not convinced? Here’s something to reflect on:
When electronic pumps get to the end of their life they die completely, and no amount of hitting or anything else will persuade them otherwise. So, when an electronic pump falters way out in the boondocks, there’s nothing for it but a long and expensive tow home. What price then an SU which a gentle tap prods into life.rubber auto oil seals Subaru.
Our experience is that it does occasionally play silly beggars with the fuel flow but not often. It seems that the only time it interrupts fuel supply is when fuel is low and the bottom of the tank is sucked up the pick-up is left high & dry on an island of tank bottom with the fuel around the edges. And the gauge is fooled – reads nearly 1/2 too! We have learned that when the fuel gauge starts to increase it’s a warning of this about to happen!rubber auto oil seals Subaru.
So in summary the non-vented cap doesn’t seem to inhibit fuel delivery when the tank is at negative pressure. And presumably the very large number of cars sold in the USA would attest to that too!
The original SU pump is very reliable for about 12 – 15 years.
Once it starts to falter, overhaul it and it will be good for another 12 – 15 years.rubber auto oil seals.
The SU pump only ever had one problem – that when it did get old and tired and falter, it would respond to a tap (which eventually becomes a hit as it gets worse) and start working again. Thus, people would not get around to overhauling it (just give it another hit), yet mutter about the unreliability (hit it again) of it every time they had to crawl under the car and HIT IT. So was born one of the great urban motoring myths! Of course it was unreliable then – it was worn out! It’s a bit like running tyres worn through to the cords and wondering why you lose the air so often!
FIX IT, DON’T HIT IT!
A new set of points and a new diaphragm (include new valves for a belts & braces approach), all correctly adjusted as per the workshop manual, and it will run happily for another 12 – 15 years. As simple as that!
Finally, (for what it is worth) avoid the electronic SU clones – I get a lot of feedback about them failing.rubber auto oil seals Subaru.
If your pump operates too rapidly, There are only five possible causes:
No petrol in tank, or faulty pick-up
If the system has been opened up – the pump is not yet primed (quite common) This can happen when it is working against air pressure and the air pressure confuses the pump’s valves) To check, disconnect the outlet hose of the pump from the pipe going forwards to the engine and operate the pump until petrol comes out the hose. If air comes out initially, this is likely the problem. Reconnect and the pump should then operate for a while until filling the carbs, after which it should slow to a click every 5 – 10 seconds as per normal.rubber auto oil seals Subaru.
Air weeping into the intake line at a joint (this is possible even though there is no petrol weeping out). Double check all joints for tightness.
Grit under the valve in the pump (sucked through from the tank) Clean out tank.
Faulty valve in the pump. Renew valve.
Not convinced? Here’s something to reflect on:
When electronic pumps get to the end of their life they die completely, and no amount of hitting or anything else will persuade them otherwise. So, when an electronic pump falters way out in the boondocks, there’s nothing for it but a long and expensive tow home. What price then an SU which a gentle tap prods into life.rubber auto oil seals Subaru.
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