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MtDewd
08-04-2002, 11:57 AM
I've recently puchased a 91 SC 5 speed with a bad motor. Now that I have rebuilt the engine, it's time for exhaust. After scanning the the forums I've noticed a lot of people are running or recommend a 2 1/2" to 3" to 2 1/2" exhaust setup. I was planning on running a 3" from manifolds to mufflers. I've ported and polished, and port matched the heads with the intent to let this motor breath. Which exhaust setup is better, 2 1/2" to 3" to 2 1/2" or a full 3"? And what about the resonator, use one or not?

Mike8675309
08-05-2002, 12:12 PM
I can't give details but I'll give garage logic.

Stolen from Flowmaster's site.

You need to try and determine your current horsepower.

Stock is around 200hp and the 2.25 to 3 to 2.25 is just fine.

Up to 300hp I would go with 2.5 to 3 to 2.5.

Keeping in mind that we want to try to maintain an even temperature through the length of the exhaust. If the exhaust cools too much before exiting, the exhaust flow could stall, increasing back pressure.

Unless you are pushing well over 300hp, I don't see a 3" true dual exhaust system as being necessary.

Some sort of cross pipe should be used. Seems like the best I've heard from anyone around here is just a simple, good resonator. It helps mellow out the sound from our V-6 that likes to sound buzzy.

68COUGAR
08-05-2002, 02:34 PM
I run the Big Dawg exhaust w/headers & no cats, no resonator. Yeah it's buzzy when I jump on it, but it flows like a sewer pipe! I don't really care what it sounds like (that's somebody elses problem!), I wanted the free-est flowing exhaust I could find. At least now, if I blow HG's, I know it isn't because of my exhaust!

68COUGAR

jpaitala
08-05-2002, 02:42 PM
I would recommend 2.5 to 3 to 2.5 system, bigger system will need enormous Hp to work correctly.

j rick kirby
08-05-2002, 03:53 PM
The stock exhaust is extremely restrictive but some people go to far the other way.Mine is a 2.25 into 2.5 into 2.25 and I'm dynoed at 320hp and 425ft/lbs.

MtDewd
08-11-2002, 02:09 PM
Thanks for the advice! I think I'll stick with a 2.5 to 3 to 2.5 until I get closer to 350 hp. Soon as I get the exhaust hung and break the motor in I'll let you know how it turns out. Thanks again!