And yet they work and have been documented to do so.....
Were they documented by an exhaust manufacturer or a magazine?
The interference does make the system quieter, and that's why they
were installed on some factory big blocks.It allowed the use of less
restrictive mufflers which could give an increase over the stock tiny
duals and mufflers the big blocks came with.
Documented by my butt! The 71 Demon I used to have had 2 1/4 all the way back with cheap turbo mufflers. Before the H pipe it would launch hard on the L-60 14s with just a little slippage. Nothing changed but adding said H pipe it would blow the tires off. Same day, same pavement no weather changes.