There have been many threads on this subject, one is even mine. I tried and failed badly at making a header, Ron I am not ! But non of these many threads seem to bring about change. A major mod for N/A Supras or the any naturally aspirated car is a header(s). Nothing is going to change if we don't change ourselves. Pacesetter, OBX, Doug Thorley: Face it guys that is old news. In my build it has come up more than once, what header are you going to use. I went as far as looking in the Lexus world and almost bought one to mod it for my Supra. I'm crazy but to buy something for $500 plus and cut it up is a stretch even for me. I read a lot have for a long time, from Car Craft to Turbo to Muscle Mustang & Fast Fords even a few Honda mags. Something that has got my attention is an article by David Vizard.
A lot of the short falls of our header design are evident after reading this article several times. One glaring thing is primary pipe size.
For me a 1 3/4'' primary is needed. I researched this and it is dead on for my setup. But a 1 5/8" pipe would give me close to the same results. But for reference the chart is pretty accurate.
Then the next question is collector style. 6 into 1 or 3-2-1 (Tri Y). It really boils down to what do you plan on doing with the car.
Then the lenth of the pipe (collector) every design I've seen is wrong. So there is more room to improve. We think we have the right set up but really we are way off. We are leaving "easy" hp on the table. We go after our exhaust system as if we had a turbo. For the most part it's okay but we need to do a few things first to capitalize on that. I'm not saying you are going to make XYZ hp by doing this. But you will make more than you do now for sure.