2.5" exhaust "upgrade?"

[Danpatters583]

I haveva 1990. I want to help increase sounds and a slight bit of Performance. I plan on removing the flash on the exhaust manifolds as well as a modern cat and better muffler. I was curious though about the 91 reatta exhaust. I was reading that on a 90 it's 2.25" and the 91 is a 2.5". If I were to find the exhaust off of a 91 will it bolt to the 90? Or is there some kind of clearance issues? I was also thinking about having a shop build a 2.5" set up for me. 

[2seater]

The larger diameter will bolt directly to the existing rear exhaust manifold. The piping may be larger but the inlet is the same. I have a '95 tailpipe that came with my donor engine and the bolt pattern matches. Just a suggestion, but in this case, I would keep the stock downpipe from the manifold, which has two nice smooth gentle bends, install a 2.5" replacement cat, even a cheap Walker universal will work fine, and then do a 2.5" cat back if you desire. Doubtful it will be worth the effort to increase size unless you are otherwise boosting/force feeding the engine. I have flowbenched the stock and aftermarket Walker universal cat and the aftermarket flows almost 50% more at the same pressure. I run that cat on my turbocharged engine. I do have a Dynomax straight through stainless steel muffler but the turbocharger takes the edge off of the sound a little.

 

Removing the restriction in the rear manifold outlet is a good idea. The rest of the manifold interior is okay as is.

[Padgett]

BTW, unless you have a really hot cam, a single exhaust is best for scavenging a 6.

[Danpatters583]

Yeah I was just going to run a single pipe. I was thinking if I can find a series one super charger set up that I would out it in the car and that's why I wash thinking of going up a size. 

 

17 hours ago, 2seater said:

The larger diameter will bolt directly to the existing rear exhaust manifold. The piping may be larger but the inlet is the same. I have a '95 tailpipe that came with my donor engine and the bolt pattern matches. Just a suggestion, but in this case, I would keep the stock downpipe from the manifold, which has two nice smooth gentle bends, install a 2.5" replacement cat, even a cheap Walker universal will work fine, and then do a 2.5" cat back if you desire. Doubtful it will be worth the effort to increase size unless you are otherwise boosting/force feeding the engine. I have flowbenched the stock and aftermarket Walker universal cat and the aftermarket flows almost 50% more at the same pressure. I run that cat on my turbocharged engine. I do have a Dynomax straight through stainless steel muffler but the turbocharger takes the edge off of the sound a little.

 

Removing the restriction in the rear manifold outlet is a good idea. The rest of the manifold interior is okay as is.

I was thinking about doing a high flow cat to help more. There was one for like 59 bucks. Haven't really decided what I want to do yet.  But thanks for all the advice!