Here's my dilemna: I just had a 3" exhaust installed using an X pipe and Dynomax ultra flows into dumps (no tail pipes). Previously, the car was set up with 2 1/2" exhaust and Dynomax super turbos. The car did not experience an off idle stumble when moving at low rpm. Since the new installation, the car has developed this off idle stumble and at cruise speed sounds like it could be detonating or popping out of the exhaust. However, I've noticed a considerable increase in power. The motor is a 383 stroker running a Demon 750. Is it possible that I need to increase the primary jets because of the greatly improved exhaust flow in order to get rid of the popping? I'm considering going up two jet sizes on the primary side. I would appreciate any advice in this regard.

383 ci
525 hp
528 tq
38 dg total advance
m21
4.56:1

You're on the right track with your thinking. You're running leaner with the improved exhaust flow. I'd try jetting up a few sizes all the way around, and increase shooter size as well. This will get you closer to the performance you were expecting. Does it cut out completely or at least cut out somewhat at higher RPM's? That's one real good indicator that you're too lean. Keep us posted.



[This message has been edited by bravewink (edited 10-10-2000).]