The F-head, more properly known as an inlet-over-exhaust (IOE) design, has the exhaust valve in the engine block driven by a low-mounted camshaft, as in a classic flat head; but the inlet valve is in the head driven by pushrods and rockers.Back in my days in the garage, I encountered this engine only once, in a 109", where the brass distributor drive gear had stripped.
Of course the first question is, if you're going to have 6 pushrods and rockers, why not 6 more and put all the valves in the head? One answer is this allows bigger valves than in anything but a hemi head; and allows higher compression ratios (perhaps) than a flat head.
The key design feature is the mating surface between block and head is not perpendicular to the bores, but at a fairly steep angle; the last photo attempts to show this seam just above the uppermost pulley.
My own Rover, a 2000 TC (or P6 in factory parlance), had the successor to the 3-litre: a 2-litre overhead cam 4 cylinder making 120 hp, an improvement on the 3-litre's 115; combined with significantly lower weight, this made the 2000 a much higher performance car. On the other hand, the full 120 hp only turned up well over 4500 RPM; the twin 2" SU carbs were way too big for the engine, making it unhappy under any condition except wide open throttle; andthe 10:1 compression ratio demanded 100 octane fuel, only available at Sunoco at the time. Not to mention the Lucas electrics ... I traded it for a '72 Chevelle with the 307 and a two-speed Powerglide transmission.
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