Editing Ford flathead V8 engine (section)

===Internal Air flow===
More extreme modifications were to improve the airflow by removing material from the top of the block between the valves and the cylinders (called ''relieving''), increasing the size of the inlet and exhaust passages (called ''porting''), and by ''polishing'' the sand-cast surfaces to improve air flow. Increased compression ratios could be cheaply obtained by milling material from the head or by obtaining aluminum heads as aftermarket parts. Higher capacity intake manifolds were similarly available. Changing the camshaft to a higher performance version required head removal so that the valves could be held up out of the way, so this was usually done only as part of a substantial rework of the basic engine.