Passing CA Smog help - High HCs

[legend57]

I'm monitoring this thread closely as I'm in the same boat. My '76 K20 has the heavy duty emissions (no EGR, no CATS), and I also went with the Edelbrock 1400 carb. I'm still building the truck, so haven't gone for smog check, but I guess I can now see the future (fail). I'm wondering if we'll need to go back to a Qjet.

NEW Chevrolet & GMC Truck, 1974-1977, 350

nationalcarburetors.com

 

[DoubleDingo]

I'm monitoring this thread closely as I'm in the same boat. My '76 K20 has the heavy duty emissions (no EGR, no CATS), and I also went with the Edelbrock 1400 carb. I'm still building the truck, so haven't gone for smog check, but I guess I can now see the future (fail). I'm wondering if we'll need to go back to a Qjet.

NEW Chevrolet & GMC Truck, 1974-1977, 350

nationalcarburetors.com

Q-Jet is way easier to pass with. I have vortec heads and associated spreadbore intake, the engine looks factory, all of the vacuum hoses are routed correctly, and with it warm, as you see, it passes with ease. Mine, like yours, has no cat, no egr, just the items shown on the air cleaner emissions sticker.

 

[DoubleDingo]

I'm monitoring this thread closely as I'm in the same boat. My '76 K20 has the heavy duty emissions (no EGR, no CATS), and I also went with the Edelbrock 1400 carb. I'm still building the truck, so haven't gone for smog check, but I guess I can now see the future (fail). I'm wondering if we'll need to go back to a Qjet.

NEW Chevrolet & GMC Truck, 1974-1977, 350

nationalcarburetors.com

And I would not recommend that NEW carburetor from National. I ordered one, it looks nice, but I sent it back as it is a giant chunk of chinesium. With all of the cr@p from China, I would not gamble on one of their cobbled-together quadrajet carburetors. Lars took one of those and tore it apart, and looked to see what it would take to get it perform like a factory Q-Jet. I forget what he had to do, but it was a lot. You'd be money better spent on a rebuilt for sure, whether from National or some other place. National is easy though.

 

[77Matt]

I'm monitoring this thread closely as I'm in the same boat. My '76 K20 has the heavy duty emissions (no EGR, no CATS), and I also went with the Edelbrock 1400 carb. I'm still building the truck, so haven't gone for smog check, but I guess I can now see the future (fail). I'm wondering if we'll need to go back to a Qjet.

NEW Chevrolet & GMC Truck, 1974-1977, 350

nationalcarburetors.com

And I would not recommend that NEW carburetor from National. I ordered one, it looks nice, but I sent it back as it is a giant chunk of chinesium. With all of the cr@p from China, I would not gamble on one of their cobbled-together quadrajet carburetors. Lars took one of those and tore it apart, and looked to see what it would take to get it perform like a factory Q-Jet. I forget what he had to do, but it was a lot. You'd be money better spent on a rebuilt for sure, whether from National or some other place. National is easy though.

Thanks! Ordered rebuild from national.

 

[DoubleDingo]

Thanks! Ordered rebuild from national.

Nice! That should get you there! It will definitely pass the visual. I didn't even adjust mine last year when I swapped on the rebuilt national carb and it passed no problem. But, since I had to do a retest, the carb before the national carb was over-fueling and I had code enforcement breathing down my neck, so it had to pass immediately, but because of the retest that passed, no less, Commiefornia deemed the truck a gross polluter. I just looked over the test results and there is nothing about gross polluter on there anymore, so hopefully I am back to every two years again.

 

[82sbshortbed]

I second quadrajet from nationalcarbureators.com mine works great. Even though I don't have to worry about emissions here in Texas. I don't like edelbrock. But that's me. Lol

 

[Dave Kay]

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.

About 10 years ago I had smog failures on my '77 C20 and the shop that did my carb rebuilding couldn't get it to pass so they put a cat-converter on it. That really dragged down the trucks performance but it passed.

You might look into having one installed on your truck and make it a BOLT-ON install so you could get a straight pipe fabbed to replace the cat-converter when you get your truck passed.

 

[DoubleDingo]

About 10 years ago I had smog failures on my '77 C20 and they shop that did my carb rebuilding couldn't get it to pass so the yput a cat-converter on it. That really dragged down the trucks performance but it passed.

You might look into having one installed on your truck and make it a BOLT-ON install so you could get a straight pipe fabbed to replace the cat-converter when you get your truck passed.

That's the problem, it'll instantly fail with anything added that wasn't on it when it rolled off the assembly line. Yes, adding a cat will make it run cleaner, but it won't help it pass, instead it'll cause it fail visual. Stupid, but true. For his truck to pass, he needs a compliant carburetor, and make sure everything is working and set/adjusted properly, engine hot, and should pass no problem.

 

[legend57]

Thanks! Ordered rebuild from national.

I just ordered one of the National rebuilt 4MV carbs, #ND4528. I'm not familiar with the Qjets, so need to research all the port connections.

 

[DoubleDingo]

I just ordered one of the National rebuilt 4MV carbs, #ND4528. I'm not familiar with the Qjets, so need to research all the port connections.

If you have the factory air cleaner, just follow the emissions sticker diagram. If not, there are a lot of emissions sticker pics in the library on the forum. Maybe there is one that is like yours. That, and plenty of members that can help here too.

 

[legend57]

I extensively researched about the smog compliant MSD fuel injection kit. I was very close to ordering one a while back, until I learned that it won't work if the truck has the smog pump that injects air into the manifolds. It messes with the O2 reading. It is too bad that options to actually make these trucks run cleaner/more efficiently are not available.

 

[DoubleDingo]

I extensively researched about the smog compliant MSD fuel injection kit. I was very close to ordering one a while back, until I learned that it won't work if the truck has the smog pump that injects air into the manifolds. It messes with the O2 reading. It is too bad that options to actually make these trucks run cleaner/more efficiently are not available.

Are you referring to this one? It says 50 state compliant.

https://www.holley.com/products/fuel_systems/fuel_injection/atomic_efi/atomic_efi_tbi/parts/2900

On Page 12 of the instructions it covers it if there is smog/air pump installed.

https://documents.holley.com/2900.pdf?_gl=1*1p2l90t*_ga*NjE3MzE3MjUyLjE3MTM4MTcxMjU.*_ga_W0HV84HP8M*MTcxMzgxNzEyNC4xLjEuMTcxMzgxNzE1Mi4wLjAuMA..

 

[DoubleDingo]

Are you referring to this one? It says 50 state compliant.

https://www.holley.com/products/fuel_systems/fuel_injection/atomic_efi/atomic_efi_tbi/parts/2900

On Page 12 of the instructions it covers it if there is smog/air pump installed.

https://documents.holley.com/2900.pdf?_gl=1*1p2l90t*_ga*NjE3MzE3MjUyLjE3MTM4MTcxMjU.*_ga_W0HV84HP8M*MTcxMzgxNzEyNC4xLjEuMTcxMzgxNzE1Mi4wLjAuMA..

@legend57 If I ever want to spend a couple grand I will be getting one of these, it should make running the engine with vortec heads in the wintertime a lot better, as the carburetor with vortecs in cold weather doesn't work well.

 

[77Matt]

That's the problem, it'll instantly fail with anything added that wasn't on it when it rolled off the assembly line. Yes, adding a cat will make it run cleaner, but it won't help it pass, instead it'll cause it fail visual. Stupid, but true. For his truck to pass, he needs a compliant carburetor, and make sure everything is working and set/adjusted properly, engine hot, and should pass no problem.

I asked the smog guy if I could add a cat and he couldn’t give me an answer one way or the other because he’d have to look it up. I am going to throw the carb on and get it dialed in and hopefully have a winner there.

 

[DoubleDingo]

I asked the smog guy if I could add a cat and he couldn’t give me an answer one way or the other because he’d have to look it up. I am going to throw the carb on and get it dialed in and hopefully have a winner there.

It'll fail if you add it. That's what the smog guy I go to told me.