Auto Racing: 1982 Ford Mustang Gt 302HO V8, inch stock, ford mustang

Question
Hi Steve,
I was wondering about backpressure on exhausts. My car came with single exhaust, but I plan to put an h-pipe on along with a Flowmaster cat back system. I think it has 1 7/8's inch stock tubing. I plan to change it to 2.5 inch tubing when I boost up the exhaust system. Different people tell me different things. Some say back pressure is a major concern and others say it doesn't matter. My car is all original except for the Edelbrock 750 carb and Edelbrock intake to match(way too big carb, but I messed up at the time thinking bigger was better, so I'm stuck with it for a while). All vacuum was removed and it is basically running on the barest of necessities. Having said that, does it matter what size exhaust I go to, 2.5, 2 1/4 or etc? And what exactly is back pressure and what does it do, according to the exhaust sytem? Thanks for your time.  

Answer
Mike-

  You should be fine with 2 1/2" tubing all the way out.  It won't kill your backpressure and it'll flow pretty well.  Backpressure is, in fact, important to an exhaust system and it's exactly what it sounds like...pressure going backwards.  Exhaust comes out in pulses and when it hits a corcked factory exhaust system part of that pulse will disipate or even turn around back to the engine.  On a street driven car it's a big worry because too little or no backpressure will cause a loss of low end torque.  So once again, bigger is not necessarily better.  Hope this helps.

Steve