My factory original exhaust is getting old and developing small leaks. I was thinking about swapping it out for the dual cat exhaust that came on the 5 speed Z28s. Will it work on my '92 RS with LO3? Will it mount up with my heads ok? It may not be available anymore. I'm assuming that I would need the entire exhaust from manifolds all the way down to the muffler. THat way it would have a factory look and hardly anyone would know it wasn't originally that way. Should add a few hp as well.
Just an idea. Any input?

 

I think your manifolds are a different diameter going into the y pipe. Not to mention, I am sure the sensors and what not are configured differently for the dual cats. I would just get a nice cat back designed for your motor rather than deal with the expense of a dual cat set up.

 

Yes it will fit, but will have to be every single piece from heads to street, like Red said. IMHO you can do better with a set of good chassis-specific headers for a 350 TPI, and a single hi-flow cat and cat-back; probably for less money, certainly less trouble, and certainly better results incuding longer life than putting a 10 to 15 year old used exhaust system on your car.

 

The exhaust manifolds are the same on both single and dual cat cars--right now my motor that had the N10 setup is hooked to a single cat factory setup w/no leaks or problems. I think the only thing that's different is the Y pipe and the diameter of the pipe where it connects to the long intermediate pipe--the dual setup is oval and the single cat is more round.

 

TonyRodz: Is your single cat system from an LO3 motor or a tuneport. I was almost certain that the LO3 motors had a smaller system than the TPI motors regardless of whether they were originally equipped with the dual cats.

 

It's from a tpi car.
I just re-read the original post--and I completely got it wrong!
Yes--the LO3 exhaust is smaller so if he wanted to swap he should get the exhaust manifolds back--not sure about the heads--I'm sure the LO3 heads are a bit more restrictive tho.
So yes--you guys were right.

 

I picked up around 3 tenths and 2.5mph swapping to L98 manifolds and dual cats on my vert (the non-G92 305s got the TBI sized exhaust in 90-92) Granted it is an L98 cammed LB9 breathing through it, but nonetheless thats a very real gain for pretty cheap compared to headers if you're just starting out.

 

Thanks everyone. So if I understand correctly...
I would need to replace the exhaust all the way back starting with the manifolds. Will L98 or LB9 manifolds fit my stock LO3 heads, though?
You are right I'm sure that using alternatives would be more cost-effective than trying to use factory pieces. I was just trying to keep a factory look. Oh well, just an idea I was kicking around.

 

The tricky part is getting the dual cats. New from GM i think they run around $900, so you need to find someone getting rid of a used set to make it a cost effective swap.

The manifolds are no big deal, any MAF TPI manifolds, or dual cat SD manifolds will work, shouldn't have to pay much more than $25 or so for these since everyone just throws 'em away when they go to headers.

In the end will they work as well as headers, no. But it'll be damn close, for less than half the price, especially on a basically stock car. Then you can take your time and save up for the good SLP headers.

As for the cat back, yes, the dual-cat cat-back is different in that it is shorter. If you look at your stock exhaust routing from the TBI exhaust you'll notice that the cat back comes out of the cat, then goes for a couple of inches, then turns to follow the driveshaft. The dual cat cat back goes all the way to that bend, and the cat back exits straight along the driveshaft there.

If you already have an aftermarket cat back you can cut it after that bend and then have it welded together there. If you need to get a cat back, then just get a dual cat piece and call it a day.