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75 smog laws

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98sub454

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La Habra, CA
Im about to buy a 75 K5 and i read that only the early models did not come with cats. the current owner said that it doesnt have cats and never did. Right now the registration on the truck has currently expired and i am afraid that if i buy it i will have to put cats on it. Is there a way to tell if the truck originally had cats? also do i need them for smog? he is telling me that i dont and i am not sure about this model year so i figured id try and ask it here.

thanks in advance

/forums/images/graemlins/k5.gif /forums/images/graemlins/burb.gif
 
Fill in your profile so we know where you are as to smog relates! And My 76 was not equipped with cats or air pump!
Bill
 
My '76 also had no cats or pump /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
 
sorry, im in socal. i figured you guys would assume ca since i am talking about smog laws. since we have smog laws up the ass
 
<font color="green"> If it was built for the CA market than it probably had cats, but if it was built for any of the other 49 states (called "federal" smog) than it didn't have them. There is a way to tell from the engine code in the VIN IIRC. I know this because I have a 78 that was built for the Washington market. No cats and it smogs fine since it is a federal vehicle. </font color>
 
My '75 never had cats or a pump. I checked the laws here in CA and found that if the GVWR was over 6000 lbs. you do not need cats or a pump, just a PCV valve and the thermostatic air cleaner. I had my truck smogged in December and it passed, no problem. Hopefully that was my last smogging!! By the time two years rolls around again, it should be exempt.

Good Luck,
Mike (#87)
 
6,001lbs and more was cat equipped, until 79 whne that changed to lower than 6,001lbs, look on your door sticker, and see what the gvw is of the truck, the Gov'y caught up to what GM was doing with increasing GVw of the 1/2 tons and rules changed in 79 so that 1/2 tons were cat'd from then on
 
ok thanks. im not too worried about it because next year it will be exempt, but i just wanted to learn more about what i was gettin into for this year.
 
75 didn't have cats, but some had the air pump which was stupid since the AIR pump doesn't do anything without a CAT. /forums/images/graemlins/thumb.gif
 
Don't think that's entirely true.

The GM car AIR applications (at least 81-87 in mid size RWD apps) divert AIR to the cat under driving conditions, but under cold engine conditions pump AIR into the exhaust manifolds, so it can further combust right there. (which is one of the reasons AIR is injected right at the exhaust port. Actually into the exhaust port, in some other GM engines)

Most of the early (prior to '84 at least) trucks equipped with AIR and cat's didn't divert AIR to the cat at all.

I don't doubt that AIR injection helps the converter do its job, but the cat isn't the sole reason AIR is there. (AIR has been around since the 60's)
 
Well I see what you are saying, but I talked to a lot of smog guys, and what their experience says is that injecting air in the exhaust isn't doing any difference except when there is a CAT that is hot enoguh to ignite the residue with the air added.
I am in no way an expert but I know my Physics and I talk to a lot of people, and so far that is what I learned.
/forums/images/graemlins/thumb.gif
I didn't know that AIR started in the 60's though, do you know in what applications?
 
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