I'm not sure whether the single cat on this car is the 3" or 2.5" diam. It looks like a 3" to me, but I was curious to know if there is some way to tell by the vin, yr model, engine that the car came with, etc. I really don't want to mess with trying to un-bolt it (it's VERY rusted, and i'm afraid I'll destroy it when removing it) until I am ready to install the new cat-back, but I need to know which one to order first...

The car is an 88 T/A and it has the TPI five liter engine and auto trans. I know it has a single cat, and I'm retty sure it's 3" but wanted to see if anyone here knows for sure because I am not that familiar with these cars (GM f bodys) yet, since I've never owned one 'til I bought this one for my son's first car last october.
Thanks,
John C.

 

No stock 3rd gen came with a 3" cat. Can you measure the cicrumfrence of your exhaust and do some simple math? I am assuming that your exhaust is the original equipment? A VIN lookup won't tell you much if a previous owner swapped parts. I would buy a 3" cat and cat-back and install them together. Chances are the cat needs to be replaced anyways and if you don't have enough money for headers than you can buy a cheap adapter to connect to your stock y-pipe and or have an exhaust shop fab it up for you.

 

Wasn't sure since this is my first GM F body. I guess that I wasn't thinking that the systems they are selling come in 2.5" or 3", and either one will bolt on to the stock cat....
Yes, but I don't think I need to now.
It is. I know for a fact that the car has the stock system with the exception of the muffler, which is a stock type replacement. I bought the car from the original owner, and he never did anything to the car except necessary maint; tires, oil and filter changes, etc. He is one of those guys that likes to keep everything as stock/original as possible. NO MODS here,...Yet..Heck, The car still has the stock AM/FM/Cassette with the EQ and bass boost!! (The original speakers are rotted out now though.)The car passed smog here july of last year (even with some bad fuel , injectors), and hasn't been driven much since then. Next year will be the last year this car has to pass a smog test, (I'll have that done next january) and after that, all the extra junk on the motor will be yanked including the cat so I want to make the one that is on there last 'til then if possible. I wanted to go ahead and get a cat-back for it because the Intermediate pipe and the muffler have a few holes rusted in them at this point.
Thanks for the info.
John C.

 

Here are the two systems that I was looking at. The first one says "1986-91 Camaro/Firebird 5.0L/5.7L with single 3" cat" Which is why I thought that the car could have come from the factory with either....
http://www.jegs.com/i/Flowmaster/389/17233/10002/-1?parentProductId=744759

http://www.jegs.com/i/Flowmaster/389...oductId=744759

 

OK, I had nice weather and a few extra minutes today, so I measured the circumference of the pipes in and out of the catalytic converter.
Here are the facts:
1) The end of the "Y" where it slips into the cat=~9.42"circumference (9.42 / 3.1412= 3" i.d. cat inlet)

2) The Intermediate pipe at the front, in the short, straight section just after the ball flange where it bolts up the outlet of the cat=~8.70"circumference (8.70 / 3.1412= 2.75" o.d. intermediate pipe)
John C.

 

OK,I looked at the links you posted and one of them is the system I'm running #17234. I even bought mine through Jegs Performance. Here's the difference I see between 5 years ago when I bought mine and what I see now.They(Jegs) are saying that it now has a Force 2 muffler( with milder interior sound and milder tone while driving but a aggressive/loud at WAT ). That was not the case when I bought mine,mine is the older 80 series muffler which is loud and aggressive all the time(inside and out). I'm going to call a few places tomorrow including Flowmaster and find out whats going on. I don't know what exactly your looking for in a muffler but there "is" a difference between the two.

 

OK,sorry,I was a "little confused" by their add so called Jegs Performance and he explained to me that the
"American Thunder" Cat back #17234 is still the same as the one that I have. Mine came with a flange that went from 3in. to a 2.5in. inorder to fit the stock Cat. Best bet is to call a Technician at Jegs before ordering just to be sure.

 

Ordered the 17233 kit today. Called and talked to a tech first, and he said they (17233 & 34) were the same except for the size of the flange at the front of the I pipe. He said that the '234 was the one I needed if my cat was 3".

 

Have you put on the Flowmaster cat back yet ? If so can you give us some feed back on how the install went and a comment on the sound.
Thanks