[ItBites]

The guy who said to put lower compression and a 114 lobe center cam is right (or the twin turbos...).

Mine used to be terribly loud with a 12.7:1 CR 427 and a 109 lobe center cam with a bunch of duration. I went to the bigger 540ci engine, but went down to 10.5:1 CR and a hyd roller cam with 114 lobe centers (248/252). This thing is WAY quieter (especially it got rid of the ear-piercing crack from the pipes) and runs on pump gas. I can talk at road speeds and be heard. It no longer hurts the ears.

It now runs a faster 10.6 sec quarter mile at 130mph as well...

The point is that the loudness, especially the ear piercing crack (which sounds great for a minute or so, btw) is as much the result of the compression and cam as it is the design of the exhaust. High compression and narrow lobe centers on the cam will always be hard to quiet down with sidepipes. With the great head designs we have today, there is little reason not to lower the compression and widen the cam lobes and still make a ton of power.