I just got off the phone with an exhaust shop and the guy told me I would probably ok with only replacing the muffler on my stock exhaust system. He said many of the cat back kits came with smaller pipes than what was on my car. It is a 3 inch pipe or 2.5 from the factory (94z28)? He also said a high flow cat is probably a waste of money on a street car. He has installed about 4 in the last 3 years and the guys came back and told him they could not tell any difference.

What do the forum members say?

 

Stock pipes are 2.5" inside diameter. The outer diameter is 2.75" roughly. A 3" inner diameter I pipe will make a pretty decent difference. Add to that, the aftermarket catback's have mandrel bent pipes. It makes a difference in flow rate, but I'm not too positive on how much of a difference. Add to that a lot of catback's are stainless steel, so they'll outlast the opti

High flow cat at this point isn't such a big deal. Later on with headers, you may want to consider it.l

 

the exhaust shop guy is insane...a 275hp car will difinatly benefit from a larger exhaust pipe!!!

and i've NEVER seen a cat back with less than 3" diameter pipe...

 

thanks for the replies guys.

 

stock inner diameter is 2.75 inches

 

Stock pipes: 2.75 ID (last I heard) necking down to 2.5 ID near the muffler with 2 1/4 ID tailpiipes. Stainless steel, Mandrel bent already. Is there going to be a difference? I dunno...lots of people have been happy just cutting off the part that necks down, and installing a 3" inlet muffler.

BTW I don't know any exhaust pipe thats 1/4" in thickness (2.75OD and 2.5ID you said)...that would be some heavy pipe!