454 dually header/exhaust question

[SCOTI]

Originally Posted by THI

If the O2 sensor is anywhere downstream you need a heated O2 sensor to operate properly (with or without a cat). If emission testing is not an issue (you mentioned no cat) I would go with one of the dual exhaust kits and get a collector that has the bung for the O2 sensor and wire in a heated O2 sensor.

The factory 454 TBI exhaust had two choke points, the factory "Y" pipe overlapped inside where the two pipes met, and the stock muffler choked down to 1-7/8" just inside of the 3" inlet. Because of excessive heat the converter was placed after the muffler. The exhaust manifolds themselves were not bad considering they had a 2-1/4" outlet. I mention this because if your system is using the original "Y" pipe cut to fit, you have the issue of the overlap at the connection of the two pipes.

This is how mine is done. 1.75 x 3" full length headers into dual 3" head-pipes; though an 'H" pipe; into 3" In/Out mufflers; then reduced down to 2.5" dual tailpipes that discharge @ the rear bed corners.