i have an 86 iroc 305 tpi bone stock(and its my intent to keep it that way). i purchased a used exhaust that i was told would fit my car. it was complete with the y pipe and was in great shape. i just left the garage where the mechanic told me that it didnt match up at the exhaust manifolds and it was a smaller diameter altogether than the original. i was bummed.. can anyone tell me why the difference?? but more importantly does anyone have any of these parts for sale?????

I think the TBI exhaust is smaller diameter. Perhaps that's what it is from?

Getting a used exhaust is always a crapshoot. Sometimes you win, sometimes you dont.

Factory exhaust was single 2.5". Are you sure whatvyou bought was from a camaro/firebird?

What i would do since you have money into it already is have a custom y-pipe fabbed up and run the exhaust you bought as a cat back until you can afford headers and proper new cat back.

TBI and LG4 used a smaller y and the downpipe on the pass side was slightly shorter. All systems used a spacer on pass side between the manifold and y. On LG4 and L69 the spacer was the EFE valve.

I did not know that.

Learn something new every day. Good to know! Thanks!

My 86 TPI Z28 had 2.75" exhaust on it. I couldn't find anything that size so I just went and got a 3" catalytic converter and custom 3" tubing. I tried the smaller 2.25" or 2.5" and it choked up the engine big time. I had a muffler guy custom mandrel bend it out of aluminum, worked way better than that smaller stuff. I wouldn't go 2.5" unless it was dual exhaust.