Passing CA Smog help - High HCs

[77Matt]

I have a 1977 GMC 5.7L 350 given to me from my dad. It passed smog no problem less than a year ago for the title transfer. Now, it failed CA smog due to high hydrocarbons (3485 ppm @ 15MPH and 1350 @ 25MPH). Also noteworthy is that the technician said the crankcase ventilation hose that feeds into the air cleaner was disconnected (it must have popped off during the inspection). I fixed the PC hose, replaced the air filter, PCV valve, plugs and wires, and rebuilt the quadrajet carb. I was going to tune it to run lean perhaps before the test. I was also going to add the emissions cleaner (not sure if the is just snake oil). It's a project truck that I'm just starting but I need it to pass smog to get moving legally. Should I do anything else before taking it back in considering its almost 100$ each test (no free retests)? and no, moving is not an option lol.

 

[CalSgt]

Change the oil before going in and take it in hot.

 

[CalSgt]

Also if they made you smog for the title transfer that’s BS…. Parent to child transfer in CA is supposed to be exempt I guess you county could be different though

 

[77Matt]

Also if they made you smog for the title transfer that’s BS…. Parent to child transfer in CA is supposed to be exempt I guess you county could be different though

He was getting ready to sell it but I wanted to take on the project so it wasnt for the parent to child transfer directly.

 

[77Matt]

Change the oil before going in and take it in hot.

Thanks - will do. 1977s do not have a catalytic converter - I was told that testing hot was for the catalytic converter. Is that true?

 

[CalSgt]

Thanks - will do. 1977s do not have a catalytic converter - I was told that testing hot was for the catalytic converter. Is that true?

Yup, heat is so the cat is active when they run the test.

A cat would probably fix your HC problem

 

[77Matt]

Yup, heat is so the car is active when the run the test.

A cat would probably fix your HC problem

Cool thanks!

 

[fast 99]

Assume is has a relatively stock cam?

High HC is anything other than excess fuel.

Could be over advanced timing to a weak EGR spring, ignition misfire, lean, ect. Vehicle does need to be warm however HC that high should be fixed. Engine is not happy.

 

[Radiohead]

A lean condition will raise HC as well.

 

[Finkaire]

I had a clogged EGR valve/passage

 

[Ricko1966]

Retard the the timing,if it's on manifold vacuum switch it to ported. Retarding the timing will let the charge burn longer because it continues to burn in the exhaust manifold after the exhaust valve opens. Terrible for milage and performance but it should clean up the pipe.

 

[Turbo4whl]

Change the oil before going in and take it in hot.

Retard the the timing,if it's on manifold vacuum switch it to ported. Retarding the timing will let the charge burn longer because it continues to burn in the exhaust manifold after the exhaust valve opens. Terrible for milage and performance but it should clean up the pipe.

These two items I recommend too!

 

[Ricko1966]

Thanks - will do. 1977s do not have a catalytic converter - I was told that testing hot was for the catalytic converter. Is that true?

All 1/2 tons 75 up should have converters to the best of my knowledge. And as @CalSgt already told you a cheap after market cat would clean it up a ton. 100 bucks a pop for the test I'd have a 80.00 cat on it. Next time I tested.

 

[77Matt]

Welp it all went south - the existing carb is shot. The fuel line threading in the carb body was in bad shape but thought I could save it with thread sealant. It was spewing fuel when I pooped the air cleaner off to tune. Bought an Edelbrock 1400 and will install in the next day or so.

I see how running lean can also raise HCs now. From what I read, they didnt put CCs on the 76 and 77 for some reason. But I will definitely look into it if it still fails. I know CA approved cats are more $$.

 

[77Matt]

I had a clogged EGR valve/passage

Did it fail for high HCs or NO with the clogged EGR?