In automotive engineering, an overhead valve internal combustion engines is one in which the entry and exit valves and ports are contained in the cylinder head. The original Overhead Valve or OHV piston engine was developed by David Dunbar Buick. It employed pushrod-actuated poppet valves perpendicular to the pistons and this is still the most common type in use. 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 technically OHV engines.
