I have owned a '77 Suburban for about 8 years, am I now having difficulty getting it to pass smog emissions. Two questions:

1) Did this vehicle originally have a catalytic converter? (mine does not)
2) Did this vehicle originally have dual exhaust? (mine does)

The big issue is whether or not my emission-control system has been "tampered" with. If anyone has reliable insight into this, I would be very appreciative. Thanks!

 

I don't know about your specific vehicle, but on Generalmotors.com in the list of things Chevrolet has introduced, it is stated "- Catalytic converters for reduced exhaust emissions in 1975"

http://www.generalmotors.com.ph/cont...TE/history.htm

 

Dual exhaust would most likely not have been a stock option from the factory, which leads me that its not the original exhaust system.

 

I think some of the 6.2 deisels did have ture dual on them. I don't know about gas though. But if you are having emissions problems and a cat would make it pass, instead of trying to make it factory and spend all the money to redo it, why not get 2 cats and put one on each side. (they should catch more off of each side, and should last longer, working only 4 cylinders apiece.

 

I had a '77 suburban for years, and would still have it except it rusted into two pieces so large I wasn't sure which one to drive away!

Though catastrophic converters were indeed introduced earlier, the light trucks did not have them at the time. The '77 with full-time 4wd had a dual exhaust (right side was specially modified to squeeze around the New Process transfer case). Mine had the 400 small block engine, but I believe the story was the same for all the engines of that year. The engine was designed for leaded gas as well, though the manual said unleaded was OK too.

Emission problems from those years usually originate with bad plugs and wires.

Regards,

David

 

Forgot to mention - emissions controls of that year (assuming it's not a California model) consisted of a solenoid to prevent vacuum advance under most conditions and idle screw mixture limiting caps. Hard to tamper with those.

If it's a California model, well...It's hard to say what they do out there!
Regards,

David