nate99

I'll probably end up registering my '81 as an antique and thus skirt any emissions requirements in Texas, but I was thinking that if I were to run cats and had it well tuned, it would probably pass the sniffer test.

What got me thinking about this was an old chevy pickup that I walked by this past weekend, and how strong the exhaust smelled. Now, I'm no tree hugger, mind you, but once I'm able to drive the car around on a regular basis, it would be nice to not smell like I just climbed out of a gas tank. As a bonus, I could likely avoid the antique registration hassle if it would pass the sensor test even without all of the other factory emission stuff gone (no EGR, no AIR pump, heat risers, etc.) if I find a shop that is not absolutist about such things.

I know newer performance cats flow a whole lot better than the old OEM jobs fromthe 70's/80's, so I just thought I'd throw that out there to the board and see if anyone had any thoughts.

FWIW, I'll never be going for max performance on the car, just a reasonably quick good looking cruiser.

Thanks.

Vetteran'81

I do not run dual cats, but this is what I heard. Please take it with a grain of salt. Running dual cats are technically illegal in pretty much every state (it's a federal regulation). Evidently, they do not work as well in pairs and thus the regulatory limitation.

If your state does a visual check, they may very well fail your vehicle simple on those grounds.

Hopefully someone with more knowledge of the subject will step in to make sure I ain't wack. Good luck!

nate99

My understanding is similar, on technical grounds. As I have heard it, the idea is, the emissions systems are designed to work in total, so if you change anything, it is tecnically not in compliance. That said, the "visual inspection" is often limited to just seeing if cats are there at all, without much heed given to number, location, etc.

I know that the hotter cats get, the better they work, so, if you divert half of an engine's exhaust heat somewhere else, you may not have enough to make it work in the first place, so why bother. That said, plenty of OEM's use dual cats, so it's likely a matter of getting the right equipment.

I'd say that it is a long shot that I would do it, but it was a thought that I had. I've got so much else to get through before that, I'm sure I'll go with whatever is most expedient to get it on the road.

Vetteran'81

Brother, I hear ya!

jb78L-82

Cats will work fine on a dual exhaust system-as long as the cats get hot enough which often means as close to the manifold as possible. The reason that dual cats on a dual exhaust is illlegal is because the car original had a 2 into 1 into 2 system with the front 2 head pipes feeding the single cat. Will dual cats work? Yes. Technically dual cats are illegal since the OEM exhaust has been alltered-Federal law-illegal. However, most states will turn the other way as long you have dual cats. Many states will not bother you at all if the car is 25+ years and older-as they should not!!! If you can get away with no cats, go for it. I have not had a cat (true duals now) for 25 years on my 78 or any emission control and have lived in NY, MA, and RI-never an issue.

taylorbg

In Texas you shouldn't have to register as antique to skirt emissions. If it is 25+ years, NO EMISSIONS. Take off the cats, go straight pipes.

jb78L-82

PS- If the carb and car are adjusted correctly, you will not smell like gasoline after driving the car. A properly tuned non emissions car will actually not have that gas fumes smell which is mostly from running too rich!

nate99

I thought that there was still a visual inspection. Perhaps since no proof of passing a test is required that the inspectors just waive it on by.

Any firsthand experience would be helpful.

Thanks.

Vetteran'81

Why not just call a local inspection station and ask?

wnmech

I am running pure duals on my 77 with no cats. Get the Texas antique plate. Five years for $50 dollars no inspection required. I dont drive my car very often and I have never been stopped by any law enforcement. If you dont drive like you should be pulled over you will be alright.

MotorHead

I put 2-3inch MagnaFlow cats on mine and it doesn't smell as bad a before. I asked the environment cop if I could run 2 cats on the Vette and he said I could, I only have to pass a visual inspection

DRIVESHAFT

Back in the late 80's, I was a state inspector in the Houston area.
Even then, cats were only a requirement on '84 and newer vehicles.
I doubt that has changed.