The valve which allows mixture into the
cylinder is the inlet valve; the one through which the spent gases escape is
the exhaust valve. They are designed to open and close at precise moments, to
allow the engine to run efficiently at all speeds.teflon auto oil seals Excellent quality.
The operation is controlled by pear-shaped lobes, called cams, on a rotating shaft, the camshaft, driven by a chain, a belt, or a set of gears from the crankshaft.Where the camshaft is mounted in the engine block, small metal cylinders tappets sit in channels above each cam, and from the tappets metal pushrod extend up into the cylinder head.mechanical oil seals. The top of each pushrod meets a rocker arm which bears against the stem of a valve, which is held in a raised (closed) position by a strong coiled spring the valve spring.
As the pushrod rises on the cam it pivots the rocker arm, which pushes the valve down (open) against the pressure of its spring. As the cam lobe rotates further, the valve spring acts to close the valve. This is called an overhead-valve (OHV) system.teflon auto oil seals Excellent quality.
Some engines have no pushrods; the valves are operated more directly by single or double camshafts in the cylinder head itself the overhead-cam system.The overhead valve system (OHV) system, operated by pushrods, has the crankshaft adjacent and parallel to the crankshaft in the cylinder block.As the crankshaft rotates, each valve is opened by means of a tappet, pushrod and rocker arm. The valve is closed by spring pressure.dust oil seals.The camshaft drive-chain sprocket has twice as many teeth as the crankshaft sprocket, so that the camshaft rotates at half engine speed.
auto oil seals. As there are fewer moving parts between the camshaft and the valve, the overhead-cam (OHC) method is more efficient and produces more power for a given engine capacity than an engine with pushrods, because it can operate at higher speeds. With either system, there must be some free play in the operating gear, so that the valve can still close completely when parts have expanded through heat.teflon auto oil seals Excellent quality.
A pre-set gap tappet clearance is essential between the valve stem and the rocker arm or cam, to allow for expansion. Tappet clearances vary widely on different cars, and faulty adjustment can have serious effects.
If the gap is too large, the valves open late and close early, reducing power and increasing engine noise.Too small a clearance prevents the valves from closing properly, with a consequent loss of compression.Some engines have self-adjusting tappets, bearing oil seals,which are hydraulically operated by the engine oil pressure.teflon auto oil seals Excellent quality.
The operation is controlled by pear-shaped lobes, called cams, on a rotating shaft, the camshaft, driven by a chain, a belt, or a set of gears from the crankshaft.Where the camshaft is mounted in the engine block, small metal cylinders tappets sit in channels above each cam, and from the tappets metal pushrod extend up into the cylinder head.mechanical oil seals. The top of each pushrod meets a rocker arm which bears against the stem of a valve, which is held in a raised (closed) position by a strong coiled spring the valve spring.
As the pushrod rises on the cam it pivots the rocker arm, which pushes the valve down (open) against the pressure of its spring. As the cam lobe rotates further, the valve spring acts to close the valve. This is called an overhead-valve (OHV) system.teflon auto oil seals Excellent quality.
Some engines have no pushrods; the valves are operated more directly by single or double camshafts in the cylinder head itself the overhead-cam system.The overhead valve system (OHV) system, operated by pushrods, has the crankshaft adjacent and parallel to the crankshaft in the cylinder block.As the crankshaft rotates, each valve is opened by means of a tappet, pushrod and rocker arm. The valve is closed by spring pressure.dust oil seals.The camshaft drive-chain sprocket has twice as many teeth as the crankshaft sprocket, so that the camshaft rotates at half engine speed.
auto oil seals. As there are fewer moving parts between the camshaft and the valve, the overhead-cam (OHC) method is more efficient and produces more power for a given engine capacity than an engine with pushrods, because it can operate at higher speeds. With either system, there must be some free play in the operating gear, so that the valve can still close completely when parts have expanded through heat.teflon auto oil seals Excellent quality.
A pre-set gap tappet clearance is essential between the valve stem and the rocker arm or cam, to allow for expansion. Tappet clearances vary widely on different cars, and faulty adjustment can have serious effects.
If the gap is too large, the valves open late and close early, reducing power and increasing engine noise.Too small a clearance prevents the valves from closing properly, with a consequent loss of compression.Some engines have self-adjusting tappets, bearing oil seals,which are hydraulically operated by the engine oil pressure.teflon auto oil seals Excellent quality.
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