if you remove the pre cats for long tube headers will you still pass pollution tests

 

This is a dangerous post, there is high probability that you and I (guilt by association) will be reminded of our responsibilities to our planet. But to answer your question, yes. Be sure the car is in good tune and hot (warmed up.) The precats are only there for cold starts. Cats only work above a certain temperature. The main cats are too far away from the engine to heat up quickly. They put the precats in when they changed from a stainless exhaust manifold to a cast iron, the stainless transmitted heat better to the cats. If you go with stainless headers (especially if they are coated) you won’t have any problems. Just FYI, if your car is in good tune (and the inside of the engine is stock, no heads / cam work,) you will pass the emission (sniff) test without any cats, but you will fail the visual (when they see you don’t have any cats.) :cheers:

 

The other thing to keep in mind is that you will be violating federal law. Probably not a big deal as I have yet to hear a case where it was enforced. Someone posted the legal language some time ago. It's pretty clear about messing with emissions equipment.

 

You won't miss'em..believe me! Check out my homepage for full TPIS header install w/o cats..... :cool:

 

Let's cut the melodrama.

Yes altering emission equipment is illegal.

Removing Pup-Cats is relatively reasonable. Get an 02 Z06 setup if you want the best flow and emission filtering.

 

If the exhaust emissions test you need to pass includes a "visual" test (such as California requires) which verifies that all O.E. exhaust emissions controls are present, then you need the pup cats--unless, of course, you've got an ignorant inspector unaware that pups came stock on the car or a friendly inspector who'll overlook their abscence.

If your emissions test doesn't have a visual and only relies on the actual tailpipe emissions to pass or fail the car, then the lack of pups will not affect the outcome.

As said elsewhere in this thread, pup cats have a practical effect on exhaust emissions only in a very short period of time after start-up. During this period, the main cats are too far down in the exhaust system to be hot enough to catalyze exhaust immediately after start-up so GM and other mfgs. use small, close-coupled, auxilary (or "pup") cats that begin the exhaust catalyzation process sooner. Because pups are closer to the engine, they reach operating temperature more quickly and begin exhaust catalyzation sooner.

However, as soon as the exhaust heats the main cats to their "light-off" temp, then the pups are irrlevant. Any IM program emissions test will only test the exhaust once the car is at operating temp, so whether the pups are working or not, won't affect that test.

Since the Federal Test Procedure benchmarks emissions on a volume per distance basis and begins immediiately upon engine start-up, anything that can be done to start the exhaust catalyzation process sooner results in an overall reduction in emissions.