So I recently bought a 91Z with low miles. The catback looks extremely clean and Ive been wondering how the heck it managed to not show signs of rust and corrosion. Im starting to think the catback was replaced at some point on this car which has 58K miles on it. Does this look like how GM joined the intermediate pipe to the ypipe? I could have swore my last 91 had a special clamp there. I was about to cut the catback off in preparation for my Magnaflow but now I think Im going to wait until it shows up so I know exactly what Im dealing with.

 

I Believe It Used A Clamp Like This.

 

Yeah its been replaced. It would have the clamp pictured above if it was oem, plus i was just under my 91 gta last night and had a good look at the exhaust.

 

It looks like the stock exhaust that has been repaired/welded in that spot, you can even see that that area was covered at one point by something else

 

Not all of the dual cat setups used the V-band clamp. Some used a slip joint with a more typical band clamp. But neither was welded together like that.

 

Yes that's defiantly been replaced / repaired at some point.

 

I haven't seen anything but the Odd ball clamp on the dual cat cars yet but I do have a NOS N10 without the special flange. Haven't looked to close at it yet to see if it was cut off by someone or not.

 

They're not too terribly common but there are definitely two designs out there. The later setup (2nd design) uses a slip joint with a band clamp, as well as the 4th gen LT1 style hanger on the intermediate pipe by the muffler. I've always considered it a mid or late 1991 change, but it could have been 1992.

Note in the diagrams below 1st Des/2nd Des. Different outlet on the Y-pipe, different clamp, different intermediate pipe.

 

That is very good info to have. Seems like quite a few small changes came out around 91.5.
It shows I have a NOS N10 (with the rpo code decals on the head shields) that's the second design.
Have a few very late 92s that I can check out to see what clamp is on them but no 90s or 91s w stock exhaust.

 

Interesting, thanks!

 

I've always chalked it up in the same category as the rough textured runners, black valve covers, blank throttlebody plate, red auto trans dipstick, orange/brown TPS connector, etc... All running changes that popped up near the end of the line.

I don't have a picture of the clamp used on the later setup, but it's the same type 1" wide band clamp like they used at the intermediate pipe to muffler on the late thirdgens and on the 93-up LT1s, just larger diameter. I'd imagine someone figured out they could save money and the flange/V-band clamp isn't the best about sealing anyway.