I am finishing up my engine rebuild and trying to figure out what to do for exhaust. It is a 396 bored 0.30 over with a Comp Cams 280S Magnum Muscle solid cam. The desktop dyno shows it will do 426 hp @ 5500 rpm's and 471 lbs of torque @ 4000 rpm's. It will have Dynomax headers and 3.73 rearend with M21 close ratio 4-speed tranny. I think I'm going with a Pypes Exhaust system. The problem I'm having is deciding between the following setups:

1) 3" X-pipe into 3" mufflers to 2 1/2" tailpipes
2) 3" X-pipe into 2 1/2" mufflers to 2 1/2" tailpipes
3) 3" X-pipe into 3" mufflers to 3" tailpipes
4) 2 1/2" X-pipe into 2 1/2" mufflers to 2 1/2" tailpipes

I am toying between the Dynomax Ultra flow or the Flowmaster 40's. I am looking for a nice sound at idle with my lumpy cam. The louder the better! The car is a 68SS Chevelle.

Would 3" tails even be fittable or have clearance problems over the axle?
Will 3" be too much and rob some of the hp and torque?
Will the 2 1/2 be too quiet?
The car is only for show and street by the way.

Help!!!

--------------------
1968 Chevelle SS
L-78 1969 396/375 hp motor
4-speed Muncie

Your (1) would be my choice, since most of the exhaust gases have cooled and are done expanding after the mufflers. The 2 1/2" tail pipes will fit nicely over the rear axle. IMHO smile.gif

i'd say 3" X pipe with 2.5" after that. the X will allow the smaller pipes to flow like they are bigger, but the smaller pipe will mellow the sound quite a bit.