Ioe engine

The intake over exhaust (IOE) engine, also known as F-head and pocket valve, is a Four-stroke internal combustion engine of primitive design used in early Harley-Davidson motorcycles. The design was also used in other motorcycles, and in car engines by various manufacturers.

The intake valves are "overhead" (located in the cylinder head) and operated by rocker arms and pushrods from the camshaft in the crankcase, while the exhaust valves are flathead (located in the cylinder or engine block) and operated by the camshaft without pushrods or rocker arms. This was a low compression design.

The ioe design allowed the use of much larger valves than a side valve or overhead valve engine, and was still being used in four wheel drive vehicles in the 1960s. (eg CJ-3B Jeep 1953-1964, 1966 Land Rover Six.)