The camshaft is the unit of an internal combustion engine that has the duty of opening and closing the valves. Working in conjunction with the crankshaft, the camshaft spins at half the speed of the crankshaft in a 4-stroke engine cycle and at the same speed in a 2-stroke engine.
4-Stroke Engine Cycle
the four cycles of a 4-stroke engine are intake, compression, power and exhaust. The crankshaft turns once for each of these steps while the camshaft does it twice. The smooth working of an engine needs precision parts and timing of the parts. There are several cams linked to one or more camshafts–one controlling the intake valve and another exhaust valve–for each piston. The intake valve is opened by the rotating cam as the crankshaft pulls the piston down. At the compression level, the intake valve is closed while the piston is pushed back up. The fuel and air mixture ignites as the piston goes downward again. Lastly, as the piston is pushed back up the cylinder, the exhaust valve is opened by the turning the cam to release the byproduct of the explosion.
A properly working engine needs precise timing between the rotation of the camshaft and crankshaft. The cams linked to the camshaft are instrumental in the harmonious opening and closing of the valves that gives an engine with its power.