32valvesftw

My 91 Z has cats that are flanged on both ends, in other words they can be unbolted and removed. Does anyone make a spool piece that fits in where the cats were? My shop won't weld straight pipe in there but they will bolt in a piece if I give it to them.

FASTAZU

If you have stock exhaust manifolds they must have been changed at some point to the later style two part manifolds as 91 were all one piece. Are you having issues with your cats? Do you think they may be stopped up?

If you want a performance gain it may be easier to go with headers and slip on aftermarket cats or no cats.

mike100

deletion of catalysts on the stock manifolds will just increase noise and pollution (not so much hp). If you want to make the pollution worth it, StainlessWorks makes stock pipe connect adapters for use with their long tube headers. This uses the factory ball flange on the driver side and they provide a slip connect for the passenger side that you can weld a 3 hole flat flange to if that is what you have on your exhaust now.

A lot of people run mini-cats on headers with pretty good luck. It will definitely be pretty loud either way.

WVZR-1

It seems like the OP already likely has headers and someone went to the effort to make the cats "removable". Each and every occurrence of this type of modification would be a "one of" and require the removal of the convertor take it to a shop or walk it around to the "back door" of the same shop and have someone fabricate the "test tube/track pipe" whatever. I doubt that both sides are actually alike either so there would be two fabrications for a tailored install.

The OP could maybe post a snapshot or three of what's there presently but I would doubt that the exhaust modification was done using the later manifolds and then adding pipes/cats. Could it be? Certainly.

OP didn't mention either how they were flanged. Were they done to match the ball/socket on the left and the three bolt flange on the right? Maybe.

I'm surprised the shop mentioned that they would bolt one in if he handed it to them. I believe one operation is as likely to be frowned upon as expensively with the EPA etc. as the other.

Many pieces of information are missing to answer the OP.

If he walks around to the "back door" of the shop he's working with he's very likely going to get an answer to whatever's needed.

32valvesftw

Thanks for the replies. A bit more information is in order, and I need to get back under the car and reconfirm. The situation is this. One of my cats is cracked and that creating a small squeaky exhaust leak until the car gets up to operating temperature. When I looked under it last, I noticed they that cats were flanged on both ends with what looked like 4 bolt flanges, could have been 3 but I don't think so. So I took the car to the shop and asked them to fix the leaking flange. They put it up, and looked ( I was not there) and determined that the leak is on top of the cat in the seam. he said he could try to weld it but thought it was going to be a PITA to get fixed. Thats when I asked him if the cats were flanged in because for a 91 they should be part of the header. I also told him what it looked like to me. His reply was the cats are definitely flanged/bolted on both ends.
What I was hoping to do was to poor boy the repair by putting track pipes in place of the cats. I used to be able to do that for my 90 stang, it was actually a factory SVO part. So I thought maybe there was a similar part for the ZR-1. It seems I was mistaken. what I will probably do is get it up higher in the air and get one of those snake cameras so I can get a better look. Anyway I read a little bit about using C5 ZO6 cat delete pipes, but they look like they would need to be modified.
One more thing, I am planning redoing the exhaust with some Corey H headers and full system back from there, maybe SW, but it will be a bit, as I need to sell a bike to get the cash, and I am finding it tough to pull the trigger on selling the bike.

RICHARD TILL

Remove the cat if needed. Clean the area to be welded with a wire brush and wire weld it. About a $50 job at the most.

32valvesftw

I took another GOOD Look under it. It is the normal stock manifolds with integral cats. Dunno what I was thinking. Anyway there is no indication that the cat is leaking to me. The 3 bolt flange appears to be leaking and has orange permatex on it. Thats where I will start by replacing that gasket if I can find one. Jerry'd does not seem to, maybe its the same as a normal C4, I'll have to look. Anyway sorry to bother you, and time for a different shop if I use one.

WVZR-1

10147973 was the OE GM# for the gasket and of course it's NLA. I'd ask if maybe someone has the adapter that was used on the 90's and have them trace that for you and then just make an appropriate one from locally purchased material.

This would only be on the RH. The LH is 3 bolt but a "ball seat" I believe.

Which side of yours is leaking?

32valvesftw

Right side is leaking. I will try to find somme garlock 900 or equivalent to use to make a gasket.