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 side-valves within the engine block.
Yale IOE engine from 1911
Closeup of two cylinders in a 3-litre Rover IOE Engine. You can see the combustion chamber, angled piston top, and exhaust valve.
An overhead valve (OHV) engine, sometimes called a pushrod engine, is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with flathead engines, where the valves were located below the combustion chamber in the engine block.
1894 prototype overhead valve Diesel engine
1904 patent for Buick overhead valve engine
V8 engine (with intake manifold removed), showing the camshaft, pushrods, and rockers