hey everyone i have the 2 1/2" dynomax super turbo exhaust on my 85 z28 (in sig). i finnally got enough money to change it so for right now i planed on gutting the cat out and put that back on. then i was going to cut off the exhaust about half way down the driveshaft tunnel and just put some glasspack style muffler on there with a turndown. im going with a 2 1/2" muffler too so keep that in mind. my main ques are... what would be the best flowing and best sounding muffler to put on it? a dynomax bullet, a moroso spiral, or a thrush glasspack. by putting the muffler with turndown on it and gutting the cat converter how much hp am i looking to gain? i also someday plan on putting a set of edelbrock headers with their y-pipe.

 

You will gain little to nothing the car will get super loude because of it being a turn down under the car and you will have ground clearance issues.

 

i'd forgotten what a dump pipe sounds like, since i hadn't driven my car in a while. i moved it on thursday, and i'm pretty dead-set on putting a full regular exhaust on it.

:shrug: ultimately, it's your decision.

 

Never "gut" a cat looking for power. You can gut it and run a pipe through it, but don't JUST gut it. That creates an expansion chamber that CREATES more air turbulence than the cat originally had I imagine.

As far as for power goes....I imagine you'd have better luck running a full 3" exhaust on the Z, as opposed to just shoving a glasspack on the current 2 1/2". Glasspacks aren't the greatest mufflers out there... But if you're set on the idea---I'd suggest either Moroso or Dynomax. Thrush is cheapo.

As far as the sound goes....well, you either love it or you hate it. My car is loud enough to wake up the whole neighborhood, with two Flowmaster 40's series mufflers dumped, but WITHOUT turndowns. I personally love the volume and the attention you get when you start your car....but the constant vibration/resonance does get irritating at times.

 

no body really has anything good to say about this set up. i thought a lot of people had this similar exhaust style on their cars with the bullet muffler and turndown. the only reason i wanted to gut the cat was because its plugged and i didnt want to puta straight pipe in place of it because its the 4 bolt cat and the pipes going into it and out of it are oval.