[Excaliber]

The book that came with my motor when I bought the car indicated a 100 horse power loss with the side pipes in place. That was when the motor was pretty radical, BIG roller cam and 12.5 to 1 compression. Unbolting the side pipes at that time was just an amazing difference in the power level you could FEEL.

Since then I've gone with a milder flat tappet cam and 9.8 to 1 compression. Now when I run without side pipes I can't really "feel" the difference. Horse power is all about breathing, where ever the "bottle neck" is where the horse power is lost. Apparently I'm not flowing near the exhaust cfm I used to and the side pipes can handle it easier.