My car has 2.25 inch exhaust with Flowmasters the were installed about 1yr before I purchased the car in '08. I wanted to put 2.5" pipes instead from the cat back. Could I just replace have the existing pipe replaced with 2.5 using a step down and step up pipe or would that cause a decrease in performance? I hate to scrap new mufflers, but I don't want to hinder my performance. Any feedback would be appreciated.

 

You are always better off to maintain the exhaust size from front to back. If you open it up in the middle only it will actually slow the exhaust flow in that section and cause a swirling effect inside the exhaust. Either do it all or don't do anything.

 

From the cat back? On what car? Your 72 doesn't have a catalyst.

 

Sorry Joe,
I meant header back...LOL Yes on my '72. Its 2.25 from there out. It seems I'll have to change the whole system to get 2.50?

 

Yes, you could do that. It is after all, your car. If you want to save a little money and use your original mufflers then do it. Any degredation in performance will be unnoticable.

I took my 71 98 to an exhaust shop and he put 2.5" pipe on from about 8" behind the manifolds (since the flange on the manifolds fit 2.25" pipe). I also had him use Thrush glasspacks that I purchased from a parts store and used one time when I started the car initially. I am very happy with the exhaust work I had done.

 

I think I can get a 2.50" kit from Summit for headache and what it would cost me to have the exhaust modified. Thanks for all the feedback guys....