I'm considering headers and true duals, but must pass emissions sniffer test for CO and HC. There's not a lot of room under there. I figure that if I do this I will use the true duals in stainless steel from Mid-America (UKPaul recommended them to me :seeya ) with mods made to the front end of them as needed to mate them up with the headers (most likely Hedman 68301-6). The ideal setup would be small cats mounted directly to the header collectors, then to the duals.

Any thoughts? :confused:

 

Do not restrict header function. Ideal for performance- mount high flow cats as far back as they will work.

 

You're saying that having the cat attached to the header collecter would interfere with the scavenging effect?

 

Ideal for performance yes, but with the cats further back it may take too long to warm up to operating temp to pass a sniffer test. I'd check with the some good CA muffler shops who have experiance with what you can get away with to avoid having to rebuild your exhaust system.

My recomendation would be mount big assed high flow cats as close to the headers as will fit on the car. Any drawbacks to scavanging should be less than using smaller, lower-flow, cats restriction.

 

Gator;

Didn't you look into a dual in dual out cat a while back, or was that another?
We theorized that the 2 - 1 - 2 system was pretty close to duals...

I'm surprised that the mid america setup would be cheaper than just going to a
muffler shop and having them run pipes. I would think that you'd make a big change
to the MID solution to hook up to the Hedman 3" collectors.

Good luck.

 

I don't know about any right out of the box that will bolt up to a collector--your shop might have to do some welding if that's what you want to try.

As for the cats themselves, find a shop that uses and/or can get Carsound converters. The company has a WWW site but doesn't sell direct. Everything I've ever read about them is that they're among the best-flowing cats out there. And the ones I've seen are fairly compact in size. Good luck.

 

My dual setup, with two monolithic cats parallel to the stock cat location, passed with flying colors. A littl ehigh on HC, but that could easily be the cause of a little bit of richness.



-Steve

 

I have a 1980 and had a similar problem. You can't do a true duals with cats on the 80-82 cars easily. Trust me, I spent months on this, and went to 5 different shops in the Phoenix area.

First off, the true-duals kit from Mid America gets pretty mixed reviews. Most people say it was a PITA to install and some had to take a kit to the exhaust shop just to get it to fit.

The only way you can do cat's with that system is to put the cats under the foot well of the driver and passenger, and that leaves you zero ground clearance and you will be able to see them under the car. Plus you will be cooking your feet and transmission.

What I had to do was swap the cross-member from a pre 1980 C3 into my car. No -- this is not a direct bolt in. The two long bolts on each side will not match up and you will have to remove the ears of the new crossmember and fabricate some new ones to make it work. For 1982's with the 700R4, just go to BowTie Overdrives and buy one of their tubular conversion crossmembers, those give plenty of room to run duals.

Once the crossmember is handled then you can run true duals from the headers, through the crossmember and mount each cat in the space where they belong (In the space behind the seats).

On my car the cat's are tucked up in there very nicely, and do not hang down at all. I also had an H-pipe added after the cats and before they pipes split to take the factory routing under the rear end housing.

The price for my system, custom made by the best shop in Phoenix was $650.
This included the pipe, an 02 sensor bung welded into the collector of the left side header, the cat's and all the work. I don't run mufflers, and kept my original exhaust tips.

If you want some photos, let me know. There is very little room under the car, so its hard to take any good pictures of the system.

Plan on this being a custom job and budget about $1000 for crossmember, exhaust work, cats and extras. This is just the price of doing the job right.

 

Cat's are not needed on my 72, but I've often thought that using a cat from (or for) a C4 might work for later C3's. My 95 has one cat, mounted mid-way, that seems to work as a 2-1-2 setup. Have cat and crossover built into one. :)