exhaust pipe diameter for a mildly modified 340

Back pressure = power loss in most anything we tested. The higher it was, the more power we lost. When none was there, the engine made the most power and the cars ran the quickest, almost 100% of the time.

My 320 HP 340 knew it had restriction but realistically, it only hurt about a tenth and 1 MPH when running 104mph and shifting at 6100.