When some one says 180's gain 30-40hp the first thing I have to ask is how much of that comes from the fact that the exhaust is far larger then the typical exhaust you can get through the suspension. We put big headers and put them through a small pipe back through big mufflers.
I would love to see a dyno with headers and exhaust the same primaries and collectors as 180's and see if there is a detectectable difference.
Second we are really talking two effects here. One is balancing out the exhaust pressure AND the harmonics of the pulse itself (scavege). The larger the exhaust and the shorter the system the less influence either of these will have.
I personally believe the 30-40 hp comes from the size of the exhaust more then the cross over pipe in a system with adequate primaries AND adequate exhaust further down. The effect of a cross over pipe will have a minimal effect with adequate pipes. Second, we have a pretty short over all exhaust system for the scavage effects to play much of a role. The effects of the scavage pulse are so pinned on cam and RPM that the effect typically improves a little on one RPM and is worse at another. The only way to know one way or another would be to actually dyno the car and change the exhaust system.
Beyound that what we are doing is largelly guesing. Which is ok. It's why we bought cars, to play with them.
And Damn, the headers Brooke is building are HOT!
Gary
