I can give you an example of what Curtis is talking about, when you just chase flow numbers, and the head is to big for the combo. A local guy, that is a friend of a friend, that chooses for some reason, to keep going back to a local head shop, recently revamped his combo. 496 cubes, 4.310 bore, Brodix BB-2plus heads, had 13.5 ish compression, 280ish .800 lift cam, etc, car ran 10.00's at 137 on a good day. The shop put in 2.35 intakes, ported the heads to 369cc, and they flowed 420, bumped the compression to 15:1, put in a 296-304 at .050, yes, at .050, .880 lift cam, and the engine picked up about 60-70hp. The car, runs exactly the same et and mph as before, and is described as "lazy". Plus, he has the added benefit of spinning the engine 8000 rpm too. It actualy ran slower the first time out, but after a new converter and more gear and 600 more rpm, it runs the same as before.