1977 K20 Heavy Duty Emissions

[blackacre]

Evening All,

My name is Johnny. I live in Alpine, Ca., just a little outside San Diego.

I picked up a K20, 4x4, automatic transmission, no rust and decent interior. The exterior is sun baked, but not too bad. The truck is a one owner prior to me and he passed away about a year back. His friend sold it to me. It was last on the road in 2002.

It runs and I'm going through it now to get it road worthy. Under the hood the only sticker left on it is the jack instructions, and the Federal emissions stickers are gone. I assume they were on the air cleaner cover.

If anyone could help me out with figuring out what the emission sticker / decal looks like, I'd appreciate it. According to a VIN lookup it's a Federal emissions truck and a heavy duty (GVWR 8400). Seeing as I'm stuck behind enemy lines, I am just thankful it doesn't have the cat and the extra burden to get it passed through the smog folks out here.

- JB

 

[legend57]

Hey Johnny. Congratulations on the K20. I got my '76 K20 about 3 years ago and have been going through restoration. I'm in the same boat with the smog. My truck didn't have any of the original equipment, so I slowly reconstructed it. It actually wasn't too bad. Here is what I learned for the '76 with HD emissions. I assume it is the same for '77, but you'll want to confirm.
* No catalytic converters required
* No EGR
* Yes on a smog pump, which means you'll need the manifolds with the air inlets, or the CARB approved headers by Edelbrock. I went with the Edelbrock ceramic coated smog legal headers. They are really nice.
* You need the thermostatic vacuum switch on the water neck. This controls vacuum to the vacuum advance, depending on water temp.
* Supposed to have the idle kicker solenoid (I don't recall the name of hand). It is a vacuum controlled solenoid that kicks the throttle slightly open under high vacuum situations. These are unobtanium. I've looked for years. You may get lucky. I have a work-around design that uses an electric solenoid, driven by a vacuum swtich. I'm not sure the smog guy will really care about that item, though. We'll see.
* Have to run the stock air cleaner with all the features hooked up. Can't recall their exact names. One is a vacuum valve and the other is the hot air valve.
* You can get a correct carb, built to the original specs (or slightly modified depending on how you plan to build your engine) from a number of Q-Jet specialists. I got mine from National Carburetor and I'm very happy with it.

The smog pump was probably the hardest item to find that was correct. Will take some searching.

I've looked and looked and haven't found the correct air cleaner smog sticker. There are a lot available, just not for the engine/year/emission level of mine. My truck has the 400 engine.

So far, I've gone through everything from the ground-up. The only thing left is to get it painted (body work is done) and install my USA1 interior (that took ~2 years to finally receive). Happy to answer any questions you have.

-Rob

 

[blackacre]

Hey Rob, nice to meet you and thanks for taking the time to write me back.

That’s interesting about the smog pump. I am hoping to avoid having to put one on. Mine came out of the Fremont plant and the intel I have seen, which I admit is tainted a bit by hopeful and wishful thinking, seems to indicate my truck was a Federal emissions truck and they didn’t push out smog pumps for these 350’s in ‘77.

It isn’t the end of the world if I have to do it but would be nice. Thanks for the tip on the Edelbrocks. That’s good info on everything.

I’m intrigued about the workaround design you mentioned. I’m in the middle of discovery learning as much as I can and may need to send a bottle of scotch or your pleasure your way and beg for a description of how that workaround works.

My sincere thanks again.

I’m keeping some notes on my progress of the build here on the forums and over at YouTube if you’re interested.

Respectfully,
Johnny

 

[blackacre]

Hey Johnny. Congratulations on the K20. I got my '76 K20 about 3 years ago and have been going through restoration. I'm in the same boat with the smog. My truck didn't have any of the original equipment, so I slowly reconstructed it. It actually wasn't too bad. Here is what I learned for the '76 with HD emissions. I assume it is the same for '77, but you'll want to confirm.
* No catalytic converters required
* No EGR
* Yes on a smog pump, which means you'll need the manifolds with the air inlets, or the CARB approved headers by Edelbrock. I went with the Edelbrock ceramic coated smog legal headers. They are really nice.
* You need the thermostatic vacuum switch on the water neck. This controls vacuum to the vacuum advance, depending on water temp.
* Supposed to have the idle kicker solenoid (I don't recall the name of hand). It is a vacuum controlled solenoid that kicks the throttle slightly open under high vacuum situations. These are unobtanium. I've looked for years. You may get lucky. I have a work-around design that uses an electric solenoid, driven by a vacuum swtich. I'm not sure the smog guy will really care about that item, though. We'll see.
* Have to run the stock air cleaner with all the features hooked up. Can't recall their exact names. One is a vacuum valve and the other is the hot air valve.
* You can get a correct carb, built to the original specs (or slightly modified depending on how you plan to build your engine) from a number of Q-Jet specialists. I got mine from National Carburetor and I'm very happy with it.

The smog pump was probably the hardest item to find that was correct. Will take some searching.

I've looked and looked and haven't found the correct air cleaner smog sticker. There are a lot available, just not for the engine/year/emission level of mine. My truck has the 400 engine.

So far, I've gone through everything from the ground-up. The only thing left is to get it painted (body work is done) and install my USA1 interior (that took ~2 years to finally receive). Happy to answer any questions you have.

-Rob

After a little digging around today, I ended up finding these two emission solutions stickers, one for a 76 and one for a 77.

 

[mlsceo]

Smog pump is no problem. Call BZ Rebuilders, Canoga Park Ca. (818) 703-0821. Super knowledgeable and
helpful, they set me up when I needed a smog pump for my 77.

 

[legend57]

After a little digging around today, I ended up finding these two emission solutions stickers, one for a 76 and one for a 77.

Wow. Your research has been more fruitful than mine has. I think that is the first HD 1976 HD emissions label I've seen. I put the image of the 1976 label into ChatGPT and am using it to generate new artwork so I can have custom labels made. I need to get the actual dimensions of the label to get the size right. Once I have that, I'll see if I can have one made in the right material. That'll be a nice touch to top off the engine compartment.

I also just learned my truck was manufactured at the Fremont, CA facility, so that is neat.

 

[legend57]

Smog pump is no problem. Call BZ Rebuilders, Canoga Park Ca. (818) 703-0821. Super knowledgeable and
helpful, they set me up when I needed a smog pump for my 77.

Right! I had forgotten their name, but BZ is where I ultimately got mine. Worked out great.

 

[Radiohead]

I also just learned my truck was manufactured at the Fremont, CA facility, so that is neat.

Mine came out of Fremont too, three years later but spec'd CA emissions. It's a big block camper special but it's label is on the radiator cover. Somewhere I have a picture of it and can go get dimensions off it if you think it will help you.

 

[legend57]

Mine came out of Fremont too, three years later but spec'd CA emissions. It's a big block camper special but it's label is on the radiator cover. Somewhere I have a picture of it and can go get dimensions off it if you think it will help you.

That would be great if you could take a pic.

 

[Radiohead]

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It's not picture quality, it really is that ratty looking. Good thing I'm out of the emissions area.

 

[legend57]

Thanks for that. I think I have found one that will work. It is the "AZ" code. It seems to check all the boxes:
* 1976
* Heavy Duty
* California Compliant
* Includes the 400 engine (Family #113)
* Indicates "AIR" for Emission Control, which is consistent with CA/HD emissions.

I've sent emails to Jim Osborne Reproductions and ECS Automotive Concepts to see if I can get a reproduction made. Hopefully at least one of them can do it.

 

[blackacre]

Rob, do you happen to know your carburetor model number? On my 77 it has a
7045583 (4mv). I assume it is the original carb, but I don’t have a smog pump.

When Jack worked on this truck, he had a lot of funny little hacks. Like, I just figured out that he put a relay in place on the wiper motor to give it a boost, I guess.

And he also welded up some protection to make sure the hood wouldn’t fold in half. The list goes on. lol. I actually kind of dig the mods, to some degree. Gives the truck character.

thankfully, I finally got my replacement condenser today and got my loser switch hooked up and new plug wires in place. Looking forward to getting a small run session before the full carb rebuild.

 

[legend57]

I got my carburetor here:

Chevrolet & GMC Truck, 1974-1977, 350"-400", Heavy Duty, Roc

nationalcarburetors.com

It isn't original, but built to be correct. The casting # is 17058213, which is for a 1978, but I've been told it is better (by Cliff Ruggles- the Q-Jet guru) than the '76.
I bolted it on and it started right up. Just adjusted the idle.

I think you asked previously about more info on the Throttle Control Valve/Actuator work-around. Here is the diagram. The Diverter Valve relates to the Smog Pump, so you won't have that.

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At high vacuum situations (high rpm with the butterflys closed), the Control Valve sends vacuum to the Throttle Lever Actuator to kick the butterflys open slightly, reducing the chance for backfire. I haven't been able to find the correct part for either the original valve or actuator. For replacements, I've found:
Vacuum actuated switch (Summit #705419-SW):

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This replaces the control valve. It is adjustable, so you have to tune it to kick on at the right vacuum level.

Then, I use an electric throttle solenoid (Standard Motor Products ES9):

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This replaces the Throttle Actuator.

For wiring, I run 12v to one side of the switch. When vacuum activates the switch, it sends 12V to the solenoid, which then kicks the throttle.
The only trick is fabricating the brackets that mount the solenoid. I haven't found one off the shelf that works. Just make sure the bracket is grounded.

Hope that all makes sense..

 

[75gmck25]

The 7xxxxxx casting carburetors are an older design that was replaced by the 17xxxxxx carburetors. As Cliff Ruggles probably explained, the newer design has a few product improvements, but both old and new will work. My '75 had the older carburetor from the factory, and I replaced it with the newer model that I pulled off an '85 Squarebody. I purchased the electric choke conversion, new throttle shaft bushings, and a rebuild kit from Cliff Ruggles. I have some upgrades on the engine (aluminum heads and a little higher compression), so Cliff provided richer jets and rods in the rebuild kit.

 

[C10MixMaster]

carb # qjet 7045583

Emissions California HD 1977
PVC positive crankcase ventilation
ECS evaporative control system (evap)
TRC throttle return control (dash pot)
CHA carburetor heated air (heated air cleaner intake)
AIR air injection reaction (air pump)
No EGR No CAT

Theres also a spark controle switch that uses port or manifold vacuum depending on temp. I think its Wells # E9121 but not 100%sure

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this was the label I had made for mine

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TRC throttle return control (dash pot) here is a pic of the TRC

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