Since the exhaust pulses alternate from one pipe to the other on an I-6 with a split manifold, some very irritating harmonics can be generated if a straight-through design muffler like a glasspack or a steelpack is used. You need a design that makes a couple of 180-degree turns with the gas flow inside the muffler. Putting a slightly larger-than-normal pipe diameter on the system like 2 1/2" in and out for both mufflers will take care of the back pressure, and stock-design baffled mufflers will control the noise. The low-restriction pipes will let a little sound escape without being annoying. I like to use two mid-1970's Cadillac mufflers, designed for enough capacity to carry the exhaust of a 500 cubic inch engine through one muffler. They've got 2 1/2" pipes in and out.
Jerry
Last edited by Hotrod Lincoln; 07/21/2008 9:26 PM.
