How Do Camshafts and Crankshafts Work Together?

Camshaft and crankshaft gears are connected by a timing chain (similar to a bicycle chain) or timing belt (similar to a drive belt, but with teeth), or are a mesh gear set (two interlocking gears) located in the “front end” of an engine. To control combustion they must be indexed (aligned to manufacturer’s specifications) to work in perfect harmony, called valve timing.

During the four-stroke combustion cycle (intake, compression, power and exhaust) the crankshaft turns twice — moving each piston up and down twice — while the camshaft turns once. This results in each valve opening one time for every two crankshaft revolutions in relation to the piston. This way, only the intake valve(s) will open on the intake stroke, both valves remain closed during the compression and combustion strokes, and only the exhaust valve(s) opens during the exhaust stroke.