Overhead camshaft or OHC, valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner, when compared with Overhead valves OHV and pushrods.
When compared directly with OHV pushrod (or I-Head) systems with the same number of valves, the reciprocating components of the OHC system are fewer and in total will have less mass. Though the system that drives the cams may become more complex, most engine manufacturers easily accept the added complexity in trade for better engine performance and greater design flexibility. The OHC system can be driven using the same methods as an OHV system, these methods may include using a rubber/kevlar toothed timing belt, chain, or in less common cases, gears.
Many OHC engines today employ Variable Valve Timing and multiple valves to improve efficiency and power. OHC also inherently allows for greater engine speeds over comparable cam-in-block designs.