bfalfa55 you know either x or h-pipe is termed a balance pipe as it provides a crossover point to equalize flow side-to-side in a V8. Engines create exhaust pulses due to firing order and to smooth out these low and high pressure pulses, a balance pipe maybe used to address the backpressure created. Backpressure simply slows down exhaust flow.
Most agree about x and h pipes and they both relate to sound and power. X-pipe is higher pitch noise and the h-pipe a deeper tone. Slight hp gain from x-pipe due to the venturi effect which allows exhaust gasses to exit combustion chamber faster (i.e. scavenging); the more cam duration, the more effective according to the experts. The 90 degree bend in the h-pipe provides more back pressure which increases low-end torque and maybe important in some cases.
My own experience 18 years ago in 1998, I bought a new Ford f150 and after a year, I had dual exhaust installed with an h-pipe. Prior to installing the dual exhaust, it ran 15.30-50s around 90mph on test night for fun. After the new exhaust, it still ran the same et/speed just over 5,500rpm. Whether you chose x or h or neither, my guess is your 55 265ci results might be similar. Although no improvement on the track, it sounded faster. Alan
