Flathead engine
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A flathead engine, also known as a sidevalve engine or valve-in-block engine, is an internal combustion engine with its poppet valves contained within the engine block, instead of in the cylinder head
A crossflow T-head sidevalve engine
1915 Cadillac flathead engine block
Harley-Davidson flathead
BMW R12
IOE engine
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The intake/inlet over exhaust, or "IOE" engine, known in the US as F-head, is a four-stroke internal combustion engine whose valvetrain comprises OHV inlet valves within the cylinder head and exhaust
Flathead engine
…seeking higher power outputs had to abandon the sidevalve. A compromise used by the Willys Jeep, Rover, Land Rover, and Rolls-Royce in the 1950s was the "F-head" (or "intake-over-exhaust" valving), which has one sidevalve and one overhead valve per cylinder. The flathead's elongated combustion chamber is prone…
Yale IOE engine from 1911
Closeup of two cylinders in a three-litre Rover IOE Engine with the combustion chamber, angled piston top, and exhaust valve visible