Here's the F head, inlet over exhaust explained diagram. This diagram is generalized for "typical" intake over exhaust design engines that were produced by many different manufacturers. The intake valve is shown only as a rocker assembly on the other side of the motor. The specific Harley designed engine has both intake & exhaust valves on the same side of the motor & the exhaust port much lower on the cylinder as well, but it's a decent explanatory diagram. Changing that sparkplug must have involved deep socket/ extension! Just a diagram after all. See the F formed by the valve (shaded F)?
Rick C.
Rick C.
Rick C.
Rick C.