Hi all, I need to get a new cat but need to know first what is the exhaust pipe size of my 85 GT?
1.75 inch? 2 inch? 2 and 1/4?
Thanks, Kit

[This message has been edited by Kitskaboodle (edited 07-14-2018).]

Most OE Fiero and new one for any car... Cats are 2" inside diam.
Pipe at the cat is 2" outside diam. Anything smaller then is neck down from 2" outside to meet needs.
2" isn't exact and often very sloppy fit.

Can get a "kit" at RA and some others w/ Cat, short pipes, and 0 to 4 clamps so you don't have to find short pipes for 4cyl Fiero. New cats are Shorter then old pebble bed cats. May need this for V6 depend how bad exhaust is.

But Note: If installed w/ clamps, Cat metal is often too tough to crush. FSM and some other books tells you slot carefully to clamp w/o big leak problems.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 07-14-2018).]

RA does not sell California cats.
I usually get them from Amazon.
Minimum price for a Magnaflow universal CARB compliant cat is $150 plus.
Ok, so the 2 inch inlet/outlet cat is the one to buy?
Thanks Ogre! Kit
P.S. As an FYI universal cats are usually weld on.

[This message has been edited by Kitskaboodle (edited 07-14-2018).]

quote Originally posted by Kitskaboodle: RA does not sell California cats. I usually get them from Amazon. Minimum price for a Magnaflow universal CARB compliant cat is $150 plus. Ok, so the 2 inch inlet/outlet cat is the one to buy? Thanks Ogre! Kit P.S. As an FYI universal cats are usually weld on.

Question Kit....first, where the hell have you been?

Next, what is the difference in CARB and Non CARB for California since the O2 sensor is on the headpipe....not the cat? I doubt anyone is going to jack up the car and look for a CARB stamp.

I see your question and I raise you one:
What happened to San Mateo? As far as I know it's still on the map.
I still have both my Fiero's but don't go on the forum as much these days.
Regarding Calif. cats, you bet your sweet bippy they check cat numbers!
Oh yes, they have mirrors at the smog shops to check them. I have been told by several smog guys to make it easier for them by keeping my cat purchase receipt in the glovebox so they don't have to check under the car.
By the way, you do realize we're talking about California here? Forget everything you know about fair and logical smog tests and you will begin to understand Grasshopper. By the way, did you know that a muffler shop cannot by law install your aftermarket cat until he has verified the number on it and that it fits your car? You cannot buy a non carb compliant cat in Calif. period!
I am convinced CARB's motto is the same as in this cartoon I saw in the paper years ago: "This ain't Burger King. You don't get it your way. You get it our way or you don't get the damn thing!"

[This message has been edited by Kitskaboodle (edited 07-14-2018).]

quote Originally posted by Kitskaboodle: RA does not sell California cats. I usually get them from Amazon. Minimum price for a Magnaflow universal CARB compliant cat is $150 plus. Ok, so the 2 inch inlet/outlet cat is the one to buy? Thanks Ogre! Kit P.S. As an FYI universal cats are usually weld on.

Only OE units are welded at car's factory. The rest simply depends who installs them and have mig/tig welding tools or not.
Read most any FSM for replacing a cat etc w/ clamps. Many GM FSM say use two slots. Even then often doesn't use same crap clamps most DIY see/get w/ weak saddles etc.
From 87 Fiero FSM...

CLICK FOR FULL SIZE

Other clamp types need slots too. Look at last picture here https://ktperformance.net/i...-i6-4-0l-409-ss.html Muffler have 4 where clamp is.

Can likely use Band Clamps but cost more... SS Band wraps around both but haven't use them.
Examples:
http://www.yogisinc.com/ind..._id=4122/prd4122.htm
https://www.ebay.com/itm/TT...-Clamp-/171060900441