Firebird90V6

Alright guys i have a few questions. I was looking into a set of headers for my 85 TA with TPI. Im being told the car has a 4 bolt cat instead of 2 like the 86 and up TPI cars. The cost of the difference is 35 bucks. I want to change the Cat and exhaust system anyways so my question is can i purchase the 86 and up header and switch to that exhaust system as well? Any help would be apprciated. thanks guys.

Morley

Should be able to, you'll need the Cat for the year exhaust you are getting, but other than that if you replace cat fwd and cat back it should work fine.

Firebird90V6

Thanks for the help if anyboyd else has any info it would be apprciated. As for now its going to be Edlbrock header kit.

Guest

Edelbrock huh.. hmm. I sure hope you are getting a good deal, because those headers arent all that great.

As for your question, get whatever you want to. The 4 bolt flange is at the front of the cat on an 85, whereas the newer ones the cat just slips over the end of the y-pipe, and its clamped in place. If you get the later model headers, you'll just need a cat for that year car as well. It'll bolt up fine otherwise.

Morley

Its on both ends of the Cat on 85's, the problem is that it was a 1 year deal (like the 870 ECM) so there are not many sources for direct bolt in exhaust systems.

jmd

iTrader: (4)

All L69 F & G-bodies used the 4 bolt front / 4 bolt rear cat, so it's not a rare item. It was also used on the 84-85 Vettes.

The cat on those vehicles is larger and will flow better than a stock 86 TPI cat - stay with your stock 85 cat.

ALSO, take note: If you order a Catco replacement cat for an L69 F or G body, you'll get a necked down restrictive POS. If you order the Vette PN, you'll get a free flowing one, just like stock.

Sorry, no pics of the necked down Catco one.

Guest

Are you sure it was both ends? Its been a while since I had my 85, but I thought the rear side was the normal 2 bolt deal like all the others.

jmd

iTrader: (4)

I'm not sure about the cat in the 85 TPI's being the L69 unit or not, although the 85 TPI F-bodies did use the L69 camshaft. But the L69 cat would be an upgrade over any other 85 or 86 F-body stock cat.

Yes, I'm sure about 4 bolts on both ends on the L69 cats.

-Matthew

Morley

Still have my '85 and it is running a high flow replacement cat atm, and yes it had a 4 bolt flange fore and aft.

Jim85IROC

iTrader: (2)

On my 85 I bought heddman headers & y-pipe for the 86+ cars, and bought a 3" dynomax universal cat. I needed to have a local exhaust shop make a short piece of pipe to connect them.

You can buy an adapter flange to hook the y-pipe directly to the 85 cat, but your exhaust choices for 85 are crap. I had to put a 2.5" dynomax on the car because that's all I could get to bolt up to the stock cat. By going with the aftermarket cat, I can use any exhaust just by hacking off the cat mounting flange and having the exhaust shop make me another short adapter piece.