rokbrigade

I would like to know something about my exhaust. I have a 95' Camaro Z-28 with a freshly built 383 Stroker. The engine has already been installed in the car. I bought BBK Headers for it but instead of buying dual CAT headers, I bought the single CAT headers not knowing it until the engine and everything was already installed. MY question: Will my car still pass a smog test with a single CAT exhaust modification or will I need to buy the dual CAT exhaust? The mechanic told me that even though I have a Dual CAT system, (the first CAT is located on the drivers side of the header and the second one is located just underneath the passenger floor pan.) the CAT that is located on the drivers side header is just a pre-CAT and that it doesn't really do much of anything except rob you of horsepower. He told me that the second CAT that is directly under the passenger side floor pan is the real workhorse which is the one that really makes the difference. I am asking you if this is true that it makes no difference. I am located in Southern California. Thank You.

Injuneer

Most 95 LT1's left the factory with a single cat exhaust system. Only the "CA Emissions" models, with the A4 tranny had dual cats. In a dual cat system, the cats are not in series (pre-cat, second cat). Your mechanic is incorrect. There is one cat for each bank of the engine. Stock location for the drivers side was bolted directly to the bottom of the exhaust manifold. Stock location for the passenger side was under the hump in the passenger front seat foot well. The "Y" branches joined after the cats.

If you have a CA emissions A4, and live in CA, you have to have both cats in place, in the stock locations. If you move the cats, or change the number or cats, you are technically in violation of Federal emissions laws, which CA chooses to enforce. IF you are in any other state (check NY and MA - they started using the CA standards sometime in the 90s), you do not have to have dual cats on a 1995 LT1.

Its possible to pass the sniffer test with a single cat, assuming the 383 is tuned correctly, and doesn't have too radical a cam. The main issue would be whether the car left the factory with dual cats, and whether you live in CA, which you do.... so you have a problem going to a single cat.

SS MPSTR

Fred is correct.

If you choose to avoid problematic (or expensive 'passes') smog inspections, get a good set of CARB EO headers (SLP's are probably the best out there for a 383), put in your cats w/ correct y-pipe, and be done with it. Be advised though, depending on how big your cam is, it may not even matter.