[cleatus12r]

I changed the exhaust on my '73 2wd about a year ago. It's had a few different setups since I started modifying it about 14 years ago.

The one I have now is the one that's staying until it gets turbocharged.

I picked up so much more midrange and top end (as if 4000 RPM is high) that it was scary for the little bit I actually did to it. (dyno proven)

My recipe for success:

Single exhaust. Sure it sounds terrible but it works. The headers never changed....neither did the first 6 feet of 3" dual pipes or the dual dynomax welded mufflers. However, immediately after the mufflers, I joined the two pipes with a "y" (not a "Y") and ran a single 3" pipe out behind the left rear with very little arch over the rear axle.

Instead of losing torque at 3000 RPM, it held absolutely rock steady up until 4000 RPM. For reference, the dyno graph for torque hit 353 ft. lbs. at 1800 RPM and stayed perfectly flat until 3500 RPM. The old setup began dropping torque at about 2600 RPM....even though it SHOULD have had better breathing.

I'm a firm believer in smooth exhaust flow....I've seen it help so many vehicles. For example, a friend's 66 Chevelle with a worn out 327 (45% leakage past the rings on most cylinders) with long tube headers, dual 2.25" pipes and glasspacks dumping in front of the front axle was a complete turd at all RPMs...it was terribly doggy.

Then (against advice from EVERY exhaust shop) he installed 3" pipe from the collectors into *cough* Flowmasters *cough* and did side exits in front of the rear tires. Did he lose any power? No. From idle all the way to redline (nearly 6500 RPM most times) he gained. It sounded terrible due to the Flowmasters, but it ran like a mad chief after the exhaust job.

You DO NOT want backpressure at all. It's a myth. If backpressure was good, stuffing a potato in the tailpipe would make your front wheel drive car do wheelies. You don't want stagnant flow either. Once the flow slows down too much, the engine has to work to push the exhaust out of the pipe.