Recommendation for cats

[GTOger]

I still have 2 years before I can run "classic" plates here in Texas, so in the meantime, I'm subject to emissions testing. The car has failed with high Nox and HC. The kicker is I got a letter from the state that tells me they won't issue new tags because the car has not passed emissions. How it makes any sense at all that our Governor will issue exemptions for coal-fired power plants, but my 39k mile Corvette is apparently at fault for killing the environment is beyond me but that's another rant for another day.

What I really want to ask is: What recommendations are out there for replacement cats for a 1990 ZR-1?

[A26B]

The problem for the 90~92, is that the cats are welded to the exhaust manifolds, like a collector section, so they will have to stay on the manifold. New cats can be added downstream but first, the old cats should be cleaned out/gutted completely, which requires removing the manifolds. Here's a photo to see how it is made.
http://jerrysgaskets.com/store2/root/images/25143612-NE.jpg

The foregoing is the least expensive. The other solutions would include buying another set of used manifolds with good cats, 90~92 or 93~95 which are listed in the parts manual as direct replacements. The other option is to toss the stock manifolds and install long tube headers & flange/clamp in cats behind them.

if you go with aftermarket cats, use only those with metallic substrate.

[Kevin]

i've had good luck with russian blues and orange tabbies...









wait wrong cats

[Fully Vetted]

I still have 2 years before I can run "classic" plates here in Texas, so in the meantime, I'm subject to emissions testing. The car has failed with high Nox and HC. The kicker is I got a letter from the state that tells me they won't issue new tags because the car has not passed emissions. How it makes any sense at all that our Governor will issue exemptions for coal-fired power plants, but my 39k mile Corvette is apparently at fault for killing the environment is beyond me but that's another rant for another day.

What I really want to ask is: What recommendations are out there for replacement cats for a 1990 ZR-1?

When I bought my car last year I couldn't even get the title transferred until it would pass. It came from a non-sniff state so it needed some work. It already had SW long tubes on it and no cats. So, I took it to Corey and he retuned it and I gave him the cheapest bullet cats I could find at Summit Racing and he installed them using the good flange connectors. I replaced the oxygen sensors and it passed. I don't know by how much it passed but it passed. Then I promptly removed the cats...:-D

[GOLDCYLON]

My advise if you need to get another 2 years try to find a set of used replacements. Trust me this is a PITA and a lot of work however for my 91 I went with a set of long tubes and randam tech hi flow cats. The car still will not pass the treadmill test. It might on a sniffer test only and I dont know what your emissions tests are like in Texas.

[Fully Vetted]

Good recommendation. Random Tech are the best you can buy. They're a little pricey but no doubt the best. If I was going to leave them on I would have gone with them but I only needed "testers" so I went cheap.

[GTOger]

There is something to be said for the removable method. You know, so you can pull the cats off for off-road use. It may be time to do the header thing. The manifolds have to come off the car either way, so.... yeah, it may be time.

[USAFPILOT]

The cheap bullet cats that came with my SW headers are causing me a headache. I can just barely pass by running 1/3 tank of 93 Oct and a quart of denatured alcohol from Home Depot. The Nox will come down when you put in the alcohol but the HC's will increase. It is all about the blend.

[GTOger]

Thanks for that, Pilot. I'd ideally like to have cats that can bolt-in/out. I wonder if there are any recommendations?

[Jagdpanzer]

Here are the temporary cats I rigged up to get through Virginia emission test.
Link to full details http://www.zr1.net/forum/showpost.php?p=117657&postcount=5

http://i540.photobucket.com/albums/gg333/pwasinger/P1000885.jpg

[A26B]

Thanks for that, Pilot. I'd ideally like to have cats that can bolt-in/out. I wonder if there are any recommendations?

Sure, install headers with flange,add short, flanged tube to each new cat and a flange on the cat-back exhaust. Then, make another flanged set of pipes only to bolt in place of the cats when not using them. You can do the same thing with slip fits & clamps, one end or both ends, but won't be bolt-in/out.

If you haven't been down to Corey Henderson's shop, Henderson Performance Technology in New Braunfels, might be a good time to go. Call & make an appointment and you may be able to wait or spend the night, while he installs the headers, fabs the cat sections and tunes the engine for the changes. Corey makes LT5 headers in his shop!

[We Gone]

I went with SW headers and 8" high flow cats, this was in 08. Have passed Ga emissions dyno (roller) and sniff test the last 5 years, all I do is change back to the stock prom and drive about 50 miles than test. Two more years and I can take them off and refab the pipes.

http://www.jegs.com/i/Magnaflow/642/59959/10002/-1?parentProductId=763223

http://imageshack.us/a/img844/5773/u9n4.jpg

[GTOger]

If you haven't been down to Corey Henderson's shop, Henderson Performance Technology in New Braunfels, might be a good time to go. Call & make an appointment and you may be able to wait or spend the night, while he installs the headers, fabs the cat sections and tunes the engine for the changes. Corey makes LT5 headers in his shop!

Hey Jerry! As a matter of fact, we have been down to see Corey a number of times. And we've used your gaskets! :dancing

Quote already in-hand for the headers, install, and re-tune on the dyno. As soon as I can convince my CFO to release the funds, I believe that is my preferred option.