There are three types of camshafts: lower, middle, and upper. The camshaft of the lower-mounted valve mechanism is located in the crankcase, the camshaft of the central-mounted valve mechanism is located at the upper part of the body, and the camshaft of the upper-type valve 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 chains, and high rigidity of the entire mechanism, making the camshaft closer to the valve, reducing the bottom camshaft caused by the larger distance between the camshaft and the valve. Waste of kinetic energy. The overhead camshaft engine has a faster valve opening and closing action, so it has a higher speed and a smoother running.