[Tom Notch]

After a good, reputable head shop (that understands a T4 head) gets done with a T4 head, there is minimal difference in the flow between any of the head styles. I used 914s cuz I got a great deal on the cores and for the improved sparkplug angle. I knew I would be having to modify or custom build exhaust for my car (a Notch with a pancake T4 that retains the useable trunk). Go up to a 44 (to 48?) intake valve and use a 38 exhaust (several people I have talked to have said the T4 exh. port won't gain any flow with bigger than 38 or 40 exh. valve, unless lots of welding and work is done to the ports). The way I got it was any bigger than 44x38 took lots more work with little gain. So above that size, the money put into them doesn't get as much improvement. The cost vs. return starts going down. It doesn't cost much difference in the parts used, valve seats and valves, but the flow improvements are more expensive for littler gains. So depending on your useage and where you want the motor to make power at (a result of cam and rocker ratio, rod length, induction, etc.) and you have to be honest with yourself about your real world driving conditions. Are you building for a street car that may see a race track once or twice a year, or an engine which you will be running on a track only? The latter would not be fun on the street IMHO. This is just the miscellaneous info I got when I was looking at heads for my application, from FAT, European, a bit of Perfomance Tech, Clyde Berg, etc. This is not the bible on heads, and I will continue to look, listen, and ask.