OHV timing is a type of piston combustion engine valve timing where the valves are located in the cylinder head, and the camshaft is located in the engine block. The designation of this type of distribution is derived from the English name Overhead Valve.

With this type of distribution, there is a relatively large distance between the camshaft and the valves. In the case of OHV distribution, the valves are therefore operated using metal lifters, lifting rods, and cams from below.

OHC timing is a type of valve timing of a piston combustion engine, in which, in addition to the valves, the camshaft is also located in the cylinder head. The designation of this type of distribution is derived from the English name OverHead Camshaft.

Usually, only a rocker arm is inserted between the camshaft(s) and the valve. Thus, The OHC distribution contains a few components, which reduce inertial forces. The disadvantage of this type of distribution is only the more complicated construction of the cylinder head.