You don't have to have giant ports to flow good. In my storage is an AFR 1034, which is a street legal head for smallblock chevies, 195cc intake runner, 2.05" valve that flows up to 280 cfm at .550 lift and 28" depression. Exhaust flow is 76% of intake flow. I sure wish they put their magic to work on LA motors!
R.
One thing troubles me, though. I seem to remember something about sonic velocity through a restriction limiting flow no matter how much delta P there was.
See
http://www.therebreathersite.nl/04_Links/Downloads/Choked.pdffor an explanation.
One area where I didn't remember correctly is that it is the velocity that stays constant, not necessarily the mass flow rate. If the density of the upstream air increases, while the velocity remains the same, the mass flow rate increases. Logically this brings us to superchargers.
