F-head engine

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The term F-head engine specifies one valve arrangement for an internal combustion engine of the Otto cycle type. In this type of engine, the intake manifold and its valves are located atop the cylinders (in the cylinder head) and are operated by rocker arms, which reverse the motion of the pushrods so that the intake valves open downward into the combustion chamber. The exhaust manifold and its valves are located beside, or as part of the cylinders (in the block). The exhaust valves are either roughly or exactly parallel with the pistons; their faces point upwards and they are not operated by pushrods, but by contact with a camshaft through the tappet or valve lifter.

This was a more expensive engine design than the earlier and more common flathead type. Its advantages included more power from its higher compression and better intake mixture flow; and greater reliability from its cooling of the exhaust valve and its spring, and having half the number of pushrods of an OHV engine.

For years the British motor car firms Rolls-Royce and Rover used this arrangement. A notable example is the Rolls-Royce B Series of military petrol engines. From 1927-1929, the American firm Hudson used a 6-cylinder engine of this form as well, but this engine is not to be confused with that of the race-winning Hudsons of the 1950s which is a conventional but efficient flathead design.

Willys and later Kaiser-Jeep made use of the Hurricane F-head design into the 1970s. This engine was the last F-head used in the U. S.

It was generally replaced by the overhead valve engine.

The term should not be confused with the Flathead engine.