New dual exhaust/emissions questions

[RegMan79]

Hey everyone, got a 79 Monte, I'm thinking of ordering a new duel exhaust and headers kit from jegs. It's a bolt on deal set up. My only issue is I live in an emissions city and my car has a cat on it. The kit has no cats and not finding one that comes with them. I don't really want them anyway (who does). Are cats typically welded on? Besides trying to find someone who lives in a non emissions town to register it there, Is there anyway around this? I can get new better flowing cats if I have to but I'd rather not. I want to do as much work as I can on my own.

 

[Ribbedroof]

If the emission inspector is a stickler for the details, no dual system will pass the visual, as no G body was delivered with a true dual system, because GM never federally certified one that way.

IMO, it should just be a sniffer test to determine if the car is in or out of emissions spec....does it really matter how it got there. Too much like right, I guess.

 

[clean8485]

Keep in mind, that if you're going to run a true dual exhaust setup on your car, that you're probably going to have some clearance issues between the left side exhaust pipe and the transmission crossmember, which will probably require either getting an aftermarket crossmember with a cutout for the left side exhaust pipe, or modifying your original crossmember to get some extra clearance for the left side exhaust pipe. As Ribbedroof has pointed out, GM never produced a '78-'88 A/G body car that had a true dual exhaust system from the factory, so they never made provision for an exhaust pipe running past the transmission on the left side of the car.
As for running an emission compliant system, you should be able to run dual aftermarket cats (check your local regulations first to be sure), that are either clamped or welded into the exhaust pipes. If you need to run a single type exhaust, you could use a system like what GM put on the later Monte SS/ Buick GN/ Hurst Olds/442. That would give you the look of dual exhausts, but be emission legal, and wouldn't require any changes to the transmission crossmember. You could either have the tailpipes exiting behind the rear wheels, or running all the way to the rear of the car.
Hope this helps. Good luck.

 

[ssn696]

I have a bunch of 3" pipe, elbows and a single cat and muffler. I was going to try to fab a single exhaust using shorty air injection smog headers and a Flowmaster Y-pipe, following the same route as the stock exhaust all the way to the stock tailpipe location. I left emissions land and went the Jegs route.

 

[Clone TIE Pilot]

In the US, non factory dual exhausts are illegal in all 50 states, even with dual cats thanks to the 1990 clean air act. If your model of vehicle had dual exhaust as a factory option for the model of engine in the vehicle, then it is ok to install dual exhaust. As stated by others above, G bodies were never certified for dual exhaust, making them illegal. I don't know about your state, but with NJ inspections, they drive the car over a camera so they can easily inspect the exhaust on a video monitor.

 

[RegMan79]

Well sh*t... I'm in Az. I think they check smog and use the sniffer. So I guess I'll be calling my uncle in another county and looking into the Trans crossmember. That really blows.. The car passed with flying colors already for the year so I have time.

 

[Ribbedroof]

Why not build a high flow single system?

 

[jiho]

If your model of vehicle had dual exhaust as a factory option for the model of engine in the vehicle, then it is ok to install dual exhaust. As stated by others above, G bodies were never certified for dual exhaust, making them illegal.

How about if you do an engine change? Same or later year Corvette setup, for example. I think that would be legal in a G-body.

 

[pontiacgp]

Check some forums in your state. There are guys who have duels in Arizona. I don't understand why you don't want cats on the car. They do nothing to impede performance unless you are constantly operating over 6,000 rpm

 

[565bbchevy]

If you just want the look of true duals you can buy a factory Monte SS exhaust system and basically be a bolt on if you already have a 305 sbc.
On my Regal which has an Olds 307 I bought the 442 factory exhaust that bolts to the catalytic and then splits off and they exit after the rear tires.