Overhead valve

In automotive engineering, an overhead valve internal combustion engine is one in which the intake and exhaust valves and ports are contained in the cylinder head.

The original overhead valve or OHV piston engine was developed by the Scottish-American David Dunbar Buick. It employed pushrod-actuated valves parallel to the pistons and this is still in use today. This contrasts with previous designs which made use of side valves and sleeve valves.

Today the technology is widespread, and the term, "OHV", is generally used to differentiate a pushrod engine from one which uses overhead cams, although both types employ overhead valves and so are both OHV engines.