differences in standard blocks?

[Stuart Giles]

Really not a good idea to have to have a length of threaded stud hanging down into the port, but most of the flow restriction on inlet ports is the so called "short side radius" i.e.the bit at the top of the inlet port where it meets the valve throat. This is pretty well a sharp right angle on A7 blocks from the factory. It's well worth putting an actual radius on this part of the port to improve gas flow.