Camshaft– better known as bump stick is a shaft used to open or close the valves in an engine for proper ignition timing, there are three configurations of camshaft.
D.O.H.C = referred to as dual overhead camshaft. Is comprised of two intake and exhaust camshaft laid next to one another to open and close the valves as set for ignition timing.
S.O.H.C – referred to as single overhead camshaft. Is comprised of one single camshaft laid below a rocker arm which when the camshaft rotates open and closes the valves.
O.H.V or pushrod – refers to overhead valve or pushrod. This is normally used in v or w engines that consists of a camshaft laid in the center between the v and w with pushrods that move up pushing on rocker arm hence opening or closing the valves.
There is a relationship between the crankshaft, camshaft and ignition timing. The valves open and close controlling the air/fuel mixture intake and exhaust which must be opened at a certain time during the stroke of a piston. Due to this the camshaft is connected to the crankshaft by a chain, belt or gears referred to as timing chain, timing belt or timing gear respectively.
If engine timing is not set properly there can be hard starting, back firing and after fire. You can have back fire i.e. the fire going through the intake manifold due to spark happening on the intake stroke. You can have after fire i.e. fire coming out your exhaust due to the spark happening in time of the exhaust stroke.
The after fires and back fires may be caused by bent valves, poor ignition timing or interchanged spark wires. Hard starting may be caused by the spark happening at the improper time during the four stroke cycle therefore Proper engine timing is essential for the long life of your car engine.