1974 K5 failed emissions. Need some advice.
 

I have a 1974 K5 Blazer at my house to fix up. I need some advise. This week the owner took it to emissions where it failed the Carbon Monoxide portion of the test. The Hydrocarbon test went fine. The Blazer has a stockish 350 with an aftermarket 4bbl carb and manifold. No cat.(but that shouldn't matter if it is running good.), but everything seems in place. Aside from maybe a vacuum leak or two that will be fixed this evening, what do I have to do to get this think to pass emissions. Thanks in advance for any help with this.

There was never a cat installed on the vehicle from the factory. The engine was originally built to use leaded gasoline.

Just curious, but what state do you live in where a 36 year old vehicle that was designed for leaded gas requires emissions tests?

Yea I thought nation wide anything older then a 75 is except.

thats what i thought also?

You can take any vehicle in for an emission test that you are willing to pay for... that doesn't mean it has to pass.
Not even in California is a 1974 model required to take an emission test. I suspect you got the new guy down at the testing place.

Nope, here in Arizona all vehicles built in and after 1967 must pass emissions. My '63 Scout is the only vehicle I own that is exempt here. Even my '71 Scout has to go. My buddy has a '67 Bronco, runs great, he's had it since High School and last year it finally failed emissions and he has had it parked on the side of his house ever since. Nobody here can believe the way it works. Even the guys down at the testing center don't think it should be this way. Taking my '71 in to emissions is ridiculous. I think the only piece of emissions equipment it has is the PCV tube. I got my '77 Jeep around this my insuring it as a "classic" but I can't do that with all of them. The Blazer isn't mine and it's owner can't register it as a classic due to the fact he has nowhere to keep it that follows the insurance guidelines.

Now, if anyone has any ideas I would like to hear them. I know some of the guys in my Scout club throw a little denatured alcohol in the tank but I am hesitant to do such a thing to someone else's truck, especially since the only people who I know that have suggested it run some of the most durable V8 engines ever produced.

well my fix was to plate my vehicles elsewhere where emissions wasnt present. i know it sucks but its still way cheaper then spending days and hundreds of dollars trying to fix stuff that may not even fix the problem. at my job i see people throw sometimes up to and more then a thousand dollars trying to get a car thats barely worth that to pass.

i used to plate my stuff in indiana and buy heavy truck plates to make them exempt. luckily illinois did away for emissions for 95 and older, which is stupid cause those would be the cars you would think need the emissions checked.

There might be some smog tech's on here that would straighten me out, but I think the timing has to be retarded to lower carbon monoxide.

I think it's hydrocarbons needs to have the mixture just a smidge rich and carbon monoxide needs the timing retarded. But it might be the other way around.

Cool, I was thinking it was the timing too. I will look into all that.

I was in the same boat as you not long ago. I ended up dropping my truck off with a mechanic and told him to get it through for me since he has the scope, but what he did if i remember right is retarded the timing, and put in a 2 barrel carb, and leaned it out (at least im pretty sure this is what he did). Then he put her all back to normal for me when he was done :) Your best bet would be just to ask an emissions repair center what they think :P they're the experts or just do what i did and tell em to give you a call when they get it through lol.