The Stovebolt Site Forums The Shop Area General Truck Talk Pollution

I'm considering buying a 70's GM truck, and would like to know what year did they start putting emission devices on engines?

If you call it an emissions device, I'd say 1957 as far as I know. Thats when the heavy duty trucks inline 6 got a positive crankcase ventilation system. I don't know about the earlier ones.

If your worried about it not having such things, you can always put a newer engine in it too.

pcv isn't a emissions device. its to ventilate the crankcase

This is true. PCV valve was tested and it greatly improved the life of the engine by taking out the acid fumes. But it also did help emissions. They just went hand in hand. If you have emissions I would call your local shop and ask. Some time in the 70's they installed a smogpump. Good luck

A GM factory PCV was first standard equipment in 1948 on the Forward Control Delivery Chassis (model 3742). It might have reduced pollution but its purpose was to protect against sludge formation and oil dilution (from low speed and start-and-stop driving). By 1953, a PVC system was an RPO for several 1-ton and larger trucks.

Oh yes it is. They don't want those vapours comming out of a road draft tube.

This is one of a trillion places that will back up my words.

http://www.businessweek.com/autos/content/dec2005/bw20051230_650527.ht

That link dose not work. Think what he ment to say was it did not start as a emission device. At first they just wanted to get the vapours out. Which is why they had the road draft tube. Then they found that the emissions at the road draft tube were just as bad as the exhaust. So they came up with the idea to run it into the engine to clean it up and so on and so forth.

Any how hope you checked with a local shop for local laws and regulations.

We had pcv on our early 50's trucks. We retrofitted smaller trucks because it did a fine job of keeping oil vapors out of the cab. Vapors out of the road draft had a habit of coming through the accelerator and starter hole in the floorboard.

I wonder if the early PCV setup was also to prevent fumes from getting into the cab with the forward control models and the COEs, seeing as how the engine was directly below.

I put a PCV system on my 51 this year. I think it is a little cleaner even sitting there idling. I have a theory that the blowby from the early high pressure combustion pushes some unburned mixture past the rings and maybe it is a little worse than the normal exhaust.

I don't consider myself an expert by any means on the subject, but I can tell you this:

PCVs went nationwide in 1962. GM offered PCV technology free of royalty to the US automobile industry. Engines were PCV equipped without any legislative requirement!

In 1968, the EPA enacted nationwide standards for tailpipe emissions.

Typically, by musclecar standards, 1971 is still a good year, but by 1972, emissions started bogging down performance.

My dads 1975 GMC truck was well-stocked with emission reducing devices. This is the first year catalytic converters were widely installed.

I think you're ok with a '70. I'd steer away from anything after '72.

Bill