When Did Chevy start using Catalytic conv. in Blazers?

[4X4HIGH]

Cats have been on most vehicles since unleaded fuel was available at least as early as 1975. Not all vehicles got Cats from the factory and i don't think it is a Ca versus Fed matter either as i've seen both with and without Cats. I do know that GVWR did play a role in what got them and what didn't.

 

[Metrodps]

1978 C20 no cat in Ohio
1979 C20 and K20 HAD cats in Ohio

My memory is not the sharpest but I believe that it was based on the GVW for the trucks. The reason I say this is because My father brought a 1 ton stake truck in 1979 also and it did NOT have a cat on it.

Best thing I can say is email GM and ask.

 

[HarryH3]

As I understood it, vehicles with a GVWR over 6000 didn't need cats until '79.

My '77 had a GVWR of 6200 and had no emmissions equipment on it.

Yep. The GVWR of the K5 was high enough to avoid the cat through most of the 70's. But as more and more people began to drive trucks, the gov't stepped up the limit so that 1/2 and most 3/4 ton rigs would have to have a cat. Pre-1979 the cutoff was at 6,000 lbs. GVWR. In '79 they raised it considerably.

 

[HarryH3]

My 88 Federal smog blazer came with no cats from the factory. Just went thru smog testing 2 months ago and passed with flying colors without cats.

Muddy, unless your Blazer was originally shipped to Canada, or had a diesel, it should have shipped with a cat. It may have somehow been deleted later, but GM would have installed one at the factory for a US gas engined truck of that vintage.

 

[TruckNutzDude]

1975