One of the biggest places for gains on my car is in the header design. I've got a standard Tri-7 4-2-1 design now on both banks (car is a TR8, 3.5 liter V8), but have a 4 into 1 on teh way with LONG pipes back to the collector.

The fabricator (who used to race a TR8 very successfully in the Playboy Endurance series in the late 80s) says he lengthened them to gain back a little torque at teh expense of top end since he was running long races.

I run sprints (45 minutes tops) and want to use the headers to move the torque curve up a bit (peak right now is at 3500 rpm) and trade a little torque (which I have a lot of) for hp (which I am a bit down on).

I understand shorten the header pipes and the pipes behind the collector will do this. However, can somone point me to a web or book resource on how to calculate the correct length of the pipes for proper tuning?

I've done some internet searching with not a whole lot of success. I want to do this right and not screw it up because these headers were not cheap.

Thanks guys.