[nkaminar]

Pete had a valid comment when he said that the ideal design was being ignored. I agree with him. The racing flat heads for the Harley Davidson and Briggs and Stratton engines are more ideal. There may have been some custom heads with more ideal combustion chamber shape, but, in my opinion, none of the ones offered today are.

The incoming air makes too many sharp turns in a flat head engine, especially a Model A engine. It starts at the entry into the block where the air has to make a couple 90 degree turns before getting to the valve. Then it makes another sharp turn to go down into the cylinder as the piston retracts. The inlet port in the block should be angled upwards towards the valve with one port for each valve. Then the part of the combustion chamber that directs the air down into the cylinder should have a generous radius and plenty of area atop the cylinder to allow an easy path for the flow. The intake manifold is another restriction, but that is another subject.