The position of the camshaft has three types: bottom-mounted, middle-mounted and upper-mounted. The camshaft of the bottom-mounted air distribution mechanism is located in the crankcase, the camshaft of the middle-mounted air distribution mechanism is located on the upper part of the body, and the camshaft of the upper-mounted air distribution mechanism is located on the cylinder head.
The engines of most production cars are now equipped with overhead camshafts. The main advantages of the overhead camshaft structure are fewer moving parts, short transmission chain, and high rigidity of the whole mechanism, which makes the camshaft closer to the valve and reduces the bottom camshaft caused by the large distance between the camshaft and the valve. The waste of kinetic energy. Engines with overhead camshafts have faster valve opening and closing actions, so the speed is higher and the running smoothness is better.