I've got an '03 Silverado with the 4.8 V-8. Just noticed today that it has dual catalytic converters going into a single muffler. Legally, can it be converted to duals or is this something that varies state to state?
if you've got dual cats (side by side, not inline) you should be fine going to a true dual, however all bets are off if ya live in California.
-Bret
Exhaust manifold going into a cat on each side going into a Y-connector and then into the muffler. All 3" pipe back to the Y (maybe all the way to the muffler). And, no, North Carolina - which is the opposite of California.
Thanks.
you're all set then. happy welding,
-Bret
Why would it matter in Cali anyways? I wouldnt think it would mess with emissions at all. Unless laws in CA say that you cant even touch your exhaust system...
This is what I was thinking, I don't live in Ca, so I don't know.. but if you leave the cats inplace.. what would it hurt to put mufflers on in a duled out fashion?
Adair
Actually, I just got off the phone with a local exhaust shop. The guy I spoke with said he's seen a TSB indicating that going straight out of the cats into mufflers would cause problems with one of the O2 sensors. Apparently, there are 4 on this truck - 2 in front of the cats and 2 behind. He also said that the pipe out of each manifold, the cats, the pipe behind the cats and the y-connector was all a single piece and modifying it would void the warranty.
Does this sound like it could be accurate?
if you kept your new mufflers at least as far away as the present flange after the "Y" I don't see how it could affect O2 function. I remember reading somewhere that mufflers should be kept 18" back from the convertor(s). as for cutting up the assembly on an '03... I think that may be a valid point. you might want to consider a split catback exhaust or a single 3" for the next 36k, then modifying it to a true dual. a single 3" would be plenty for a 4.8, hell it's fine for a mild 5.7.
HTH, Bret
You can do pretty much what you want to your Exhaust after the Cats in California. If your Car/truck has the Engine Exhaust from into a Single pipe into the Converter, you can't make it a Dual system and install 2 converters for example. Like say on my 03 Silverado, with the 5.3L in it. The Exhaust goes into a Single pipe and though the Converters, into the Muffler and out to the right side of the truck. I work in a muffler shop in California, first thing I did is Cut off the Exhaust system. From right in front of the Muffler on back. Installed a Flowmaster 50 series Single in Dual 2 1/2" out Stainless, Stainless Pipes all Custom Bent, coming out the Back on each side of the Trailer hitch, with some Stainless Rolled Angled tips. About a $600 Job, FREE for myself. Sounds great, and with the K&N FIPK Intake kit(Which I got FREE also) is runs great. I notice the performance doing this.
In fact we get brand new trucks, mainly Chevy's/GMC's and chop that stock Exhaust system right off. Some weeks we have a pretty good collection of Brand new stock Chevy Mufflers that just get tossed for scrap! We do some of the Dealers in the Area also on different packages, for things like Lowering Jobs, grills, 20" wheels and exhaust setups. We don't get into the Hard core Sport truck look, just something to make a stock truck look and sound a little different then stock. You can see a Picture of My own personal truck here at
My brother bought a used 2000 Ford Step side about 3 days after buying my new truck, and we did pretty much the same type of thing on his truck. Different grill, wheels, and he got a Hard Bed Cover, and also got Clear front headlights and clear turn signals. He also got a Regular Flowmaster setup, not Stainless, except for the tips.
Looks a 1000 times better. The last owner of the truck had some Gay ass stuff installed and was the first thing removed. Things like Door trim. You know that crap you push on and wrap around the door edge, so that when you open you door and slam in into something you don't scratch/chip your paint. The stuff was silver in color on his Red truck. LAME. Having a Stock Car or truck is LAME!!!!!!!!! My truck sure is not stock, my Harley is NOT stock, and my Jetski is NOT stock!
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