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.

Valve timing is a mechanism using valves to control the flow of working gases (air, fuel, exhaust gases) through a piston combustion engine. This is the most common type of mechanical distribution, used mainly in four-stroke internal combustion engines.

The opening of the valves is controlled by the respective cam of the camshaft, which is driven by the crankshaft. In four-stroke engines, the camshaft rotates 2x slower than the crankshaft, because one working cycle of the engine takes two revolutions of the crankshaft.

The camshaft is the shaft that opens the intake and exhaust valves of the internal combustion engine, thus allowing the filling or emptying of the cylinders. A camshaft is a rotating lever on which the cams are located.

The number of cams on the camshaft depends on the number of cylinders in one row of the engine and the number of valves per cylinder.