This is probably a general engine theory 101 question and I'm looking for tuition . I have a '73 HLS30 with a standard E88 head on a P30 block (I have no idea if they've been previously molested/machined in any shape or form though). I'm doing some future planning and dreaming and I'm looking at inlet manifolds such as the Magoletsi, the Harada and Jenvey's offering. The inlet ports on the E88 head measure at 34mm but the Jenvey manifold is 40mm diameter at the manifold runner exit. I can't find cylinder head port dimensions for the Mangoletsi or the Harada (small or large) at the minute though. Shouldn't the inlet manifold runners match the port size on the head? Wouldn't a situation where the runner diameter is greater than the head port diameter cause turbulence on the airflow? Does it even matter? Is it just that the Jenvey offering is only suitable for other heads and the Harada/Mangoletsi would be suitable for me or do I need a different head? I don't mind spending money - just ask my wife . Thanks. Jon.