In the 87 Vette, we have 2 pre-cats and a Cat before the "Y" pipe. Are all 3 cats necessary? I saw in ecklers an exhaust system without the pre-cats, is this an upgrade? Does it interfiere with the "Smog Check "?...yes Im in California
Just to let you know it is a felony to tamper with the factory exhaust per the EPA Clean Air Act. Better to leave well enough alone. If they are bad or the car has over 50k miles then you can replace them. I am sure you can find free flow replacements.
For some it works...others it does not. I changed my stock system to all stainless with Borla cat back and was able to reduce the resonance dramatically. In addition to that I used duct insulation, 1/4" foam with a aluminum foil on one side sticky on the other, and layered the inside with it. Not only did it reduce the sound but also reduced the heat factor.
The Cali Smog stations will catch it and you'll flunk. Go with free flows like Eagle suggests. Whatever you replace make sure it has a CARB number approving it in Cali.
Now on a different note. Is the car plated in Cali or your home state? If it is your home state what are their requirements smog wise for you to renew the plates in that state? Most allow active duty guys to renew by mail. Texas does.
Now I am not suggesting in any fashion that you violate federal law, be charged with a felony and ruin your career, but it may be easier to use your home state tags which have an easier or no smog check requirement to get 'around' the Cali smog check. One of the 'bennies' of being active duty.........
Actually Eckler or Mid America does sell a system that is CARB or O.E. not sure which, not sure if it's 48 state or 50 state legal. But it is legal according the ad. I think it was made by Walker or Dynomax?
I'm not sure how they do this if part of the inspection is visual. It's a plain front y-pipe with a 3-way main cat and comes with paper work stating it's a valid replacement. On the original OEM exhaust it's also a 3-way system exhaust but the main cat is a 2-way cat. The pre-cats are 1-way. What you can do is cut open the pre-cat case and hollow out the pre-cats. Or you can cut the pipe at the pre-cat, blast out the media in the center only and insert and weld a small piece of properly size exhaust pipe so that if flows slightly better. Then buy a 3-way main cat. Keep in mind this is still tampering. I bought a Random Technology cat. That way you'll still pass the visual and still be running clean as a whistle.
Note: don't breath in the cat media, use a proper mask.
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