In some engines, a single camshaft operates the intake valves, which allow the air-fuel mix into the engine, and the exhaust valves, which allow the air-fuel mix to escape after combustion. With an overhead-camshaft engine, camshafts are mounted in the cylinder head, above the valves. How this is done and how many camshafts are involved depends on the type of engine. As the camshaft rotates, the lobes contact other parts that activate the valves and move the air-fuel mixture in and out of the combustion chambers in a well-choreographed sequence that repeats itself hundreds of times each minute. To open and close the valves, a camshaft has egg-shaped lobes - or cams - mounted on a shaft.

Related: Is Your Check-Engine Light On? 5 of the Most Common Causes Every roadgoing production car engine has at least one, and many current engines have two or more. Cam is shorthand for camshaft, the engine part that opens and closes the valves to let the air-fuel mixture in and out of the combustion chambers.

How an engine cam works