In addition to furnishing power for the various engine accessories, the drive mechanism provides the
power that operates the engine valves. The basic job of the valve actuating gear is to cause and to control the
opening and closing of the inlet and exhaust valves. In most engines, this gear consists of rocker arms that
actuate the valves, push rods that connect the rocker arms and the cams on the camshaft, and a drive that
connects the camshaft to the crankshaft.