[lt1silverhawk]

1977 Chevrolet C/K Series Truck: Identification and Smog Equipment Verification

Hi All,

I have a 1977 Chevrolet truck. It does not have a VIN plate on the driver-side dash nor does it have a data plate on the driver-side door jamb under the striker. In place of the data plate, there is an "Assigned Identification Number" plate from the state of California with the VIN and a control number listed. Also, there is a sticker listing the RPO codes.

When I took my truck for a smog test, I was told by the tech that because my truck does not have an EGR valve (aftermarket intake with no provisions for EGR), my truck would not pass the visual inspection test. He confirmed in his guide book that this truck with a 350 is supposed to have an EGR valve. I have not yet gone for a second opinion.




The issue of the lack of EGR valve, VIN and data plates came up in another thread and several forum members have been helping to the best of their abilities to find out what this truck should and shouldn't have from factory. If you know of any sources or have any first hand knowledge on how to find out what the factory smog equipment was, please do chime in.

According to the VIN, the truck is a Light Duty Chevrolet Conventional Cab 4x4, 350 165 HP 4 bbl, 3/4 ton, Cab and Pickup Box or Van with Hi-Cube. Please click here to see what the factory codes were for this model year (thank you cobalt327).

According to the RPO codes, the truck is a K20 4wd with 350 V8, TH400 transmission and 4.56 ratio rear axle. Please click here to see what the data plate looks like (thank you 75gmck25).

Thanks in advance :thumbup:

 

[KMatch]

All you're asking for really doesn't mean anything - if the state inspection manual lists it differently. As a Texas inspector, the manual is our bible. If it shows an EGR being required, it had better be there with no visible modifications to disable it. See if you can get a copy of that section of their manual. It may show some loopholes, ie, not needed above a certain gross weight, etc. You're likely going to have EGR before it's all over, but their manual is the place to find the info you need.

 

[lt1silverhawk]

Hey KMatch,

All you're asking for really doesn't mean anything - if the state inspection manual lists it differently. As a Texas inspector, the manual is our bible. If it shows an EGR being required, it had better be there with no visible modifications to disable it. See if you can get a copy of that section of their manual. It may show some loopholes, ie, not needed above a certain gross weight, etc. You're likely going to have EGR before it's all over, but their manual is the place to find the info you need.

I agree. Chances are that by the time this is all said and done, there will be an EGR and another manifold sitting in the truck. Some of the forum members, including yourself, have mentioned that the EGR may not be needed if the vehicle is over a certain gross weight. At this point, I don't know the weight. In another thread, cobalt327 brought up the point as to why would the previous owner ditch the EGR valve but retain the rest of the emissions setup.

I'm gonna pay the shop another visit tomorrow and see if the tech will let me see and maybe even make a copy of the section dealing with this truck. Would you happen to know if such manuals con be purchased by consumers?

Thanks for the help :thumbup:

 

[KMatch]

I don't know about buying the manuals, but a good bit of the Texas version is online at the state site. Look up your local DMV sites for a starting place and see if they offer info as if you were looking to become an inspector. From there you may find some more info including possibly manuals.

 

[lt1silverhawk]

While I was unable to find a manual on the the DMV or the BAR (Bureu of Automotive Repair sites), I did find other techincal information, including making an appointment for a referee to get a new label made.

The site also has a place to check vehicle's smog test history. I don't have the VIN on hand but I will see if this gives any relevanrt info tonight.


I also found some info relating to weight in the "Smog Check Reference Guide":

Vehicle classes

For the purposes of this Appendix, vehicle classes are defined as follows:
"Passenger Car" (PC) - any motor vehicle designed primarily for transportation of persons and having a design capacity of 12 persons or less. "Light-duty Trucks" (LDT) - any motor vehicle rated at 6,000 lbs. GVW or less which is designed primarily for purposes of transportation of property or is a derivative of such vehicle, or is available with special features enabling offstreet or off-highway operation and use.

"Medium-duty Vehicles" (MDV) - any pre-1995 heavy-duty vehicle having a manufacturer's GVW rating of 8,500 pounds or less, or any 1995 and later model year heavy-duty vehicle having a GVW of 14,000 pounds or less, or -any low emission vehicle having a GVW greater than 6000 lbs but less than 14,000 pounds. Manufacturers may elect to certify pre-1995 vehicles up to 10,000 pounds as medium-duty vehicles.

"Heavy-duty Vehicles" (HDV) - any motor vehicle having a manufacturer's GVWR greater than 6,000 pounds, excluding: light-duty trucks and 1978 and later medium-duty vehicles and 1995 and later vehicles less than 14,000 GVWR. Manufacturers may elect to certify pre-1995 vehicles up to 10,000 pounds as medium-duty vehicles.

Attached below are the documents I used.




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Found some information on the DMV site regarding "Assigned Identification Number" plate here:

The VIN is the number by which the vehicle is registered. The numbers are assigned by DMV or CHP (from DMV referral) for motor vehicles when the motor or other identifying number is removed, destroyed, or obliterated. DMV assigns VIN plates to trailers under 6,000 pounds unladen, trailer coaches, special mobile equipment, implements of husbandry, new motorcycles (except specially constructed) and snowmobiles.

Statutory Authority: VC §4166

This information would lead me to believe that the truck was either rebuilt or recovered from theft. However, it has a clean (non-salvaged) title.

 

[joe_padavano]

Let's back up. What you need to be able to prove is what emissions equipment came on the truck from the factory. Unfortunately, without the original VIN, you have no proof as to what this truck was originally. The SPID that you showed indicates that the truck is a 3/4 ton (the CK20903 at the top of the equipment listing indicates a 3/4 ton). I'm pretty sure that a half ton came with an EGR valve. I'm not sure about a 3/4 ton. Perhaps someone has a 1977 factory service manual and can elaborate.

 

[joe_padavano]

OK, more info. A 1977 Chevy 3/4 ton with 350 DID come from the factory with an EGR valve. Sorry.

 

[lt1silverhawk]

Hey Joe,

Can you tell me where you found the info? Thanks for the help! :thumbup:

 

[lt1silverhawk]

Found some unofficial but interesting info on this site. These boys are in California too and the thread is from last year. I picked up on the following posts for some leads:

...Years ago my dad had a '77 "heavy half". No cats, no EGR, no air pump. Stock! He had an edelbrock manifold with the correct Q-jet. Passed smog every time.

SOME 1/2 ton pickups, blazers and suburbans in Ca in 76 and 77 didn't come with a cat, even though they were 1/2 ton chassis if ordered with heavy duty suspension like a tow package or a camper package it came with a heavy duty 350 or 400.So it only needed PCV, TAC, single EVAP canister and Air injection. NO EGR, NO CAT. 3/4 ton trucks same thing. Big Block trucks needed EGR and Air injection. My 76 GMC 1/2 ton stepside was a Ca truck, no EGR, no Cat, only Air injection. Same for my dad's 76 suburban. Both were heavy duty suspension packages. Any experienced smog tech will know that, also the emissions application book they have should show that too.

One of the members in the above-mentioned forum also posted on Hotrodders here.

 

[lt1silverhawk]

Hi All,


While working on the truck this past weekend, I discovered that the air filter housing has a device installed on the floor, and it also has two nozzles underneath it. There is nothing connected to it. (First two pictures)


I also found a couple of hoses grouped together using a metal bracket of sorts (bottom picture). One of the hoses has been connected between a speed actuator pump device IIRC, and the carburetor. The other hose isn't connected to anything. But they look like they might connect to the device inside the air filter housing.


My questions are: a) what is the device inside the air filter housing and what does it do; and b) would/should the two hoses be connected to that device?


Thanks in advance.

 

[Jim Rockford]

That sensor on the air cleaner is a thermo valve for the air cleaner heater flap, one side should be manifold vacuum and the other line should go to the round housing on the air cleaner snorkel, its suppose to keep the air to the carb at a certain temp by either letting more cool fresh air in or closing the flap and drawing air from the manifold heater thorough a metal foil tube running to the bottom of the air cleaner snorkel from the passenger side exhaust manifold.

(TAC) An air cleaner which also controls the temperature of the air entering the engine. A temperature control is necessary to optimize the air/fuel ratio with regard to minimum exhaust emissions; typically, the TAC regulates air intake temperature at about 27-46°C by means of a control damper that mixes pre-heated air from an inlet at the exhaust manifold with air from a cold air inlet; designs for actuating the damper range from simple thermostatic action to vacuum-motor and stepper-motor control

 

[123pugsy]

Holy cow Hawk!

Ten months to get back to your poor truck?

 

[lt1silverhawk]

Hey Jim,

That sensor on the air cleaner is a thermo valve for the air cleaner heater flap, one side should be manifold vacuum and the other line should go to the round housing on the air cleaner snorkel...

So, the two paired-up hoses that I have might be the ones to do just that? The one running from the carburetor possibly being manifold vacuum? I took the image below this morning after briefly reading your post. The connected hose is coming from the carburetor at this point.

...its suppose to keep the air to the carb at a certain temp by either letting more cool fresh air in or closing the flap and drawing air from the manifold heater thorough a metal foil tube running to the bottom of the air cleaner snorkel from the passenger side exhaust manifold.

Got it. I know there is a metal foil tube sitting around in the cab. But this truck doesn't have the exhaust manifold heat shield. Below is picture of the manifold from from my truck on another thread. Maybe the manifolds were swapped at some point, or the air filter housing is from another vehicle?

[/QUOTE]
Thank you very much for the image! :thumbup:




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Hey Pugsy,

Holy cow Hawk!

Ten months to get back to your poor truck?

I thought you said not to touch it until I got better at not dropping bolts in weird places. That's how long it took lol!

The "poor truck" indeed. We've had some "adventures", the latest one is figuring out why I have to revv the heck out of the engine lately just to get it running and shifting right: "1977 Chevy K20: Engine Suffers from Hesitation/Power Loss When In Drive". Don't know if it is ignition-related, or the sticky fast idle cam is to blame.

And its rust spots are becoming more and more obvious. I'll be posting pictures in the Exterior section soon to get some feedback on whether it is salvageable by a rookie Yours Truly, or has its time come to go to car heaven.

 

[lt1silverhawk]

Hey Jim,

So, the two paired-up hoses that I have might be the ones to do just that? The one running from the carburetor possibly being manifold vacuum? I took the image below this morning after briefly reading your post. The connected hose is coming from the carburetor at this point.

Sorry, the image was never attached. here it is below:

 

[123pugsy]

Without the heat riser from the manifold, you can remove the hoses and cap off any vac ports they come from.

 

[lt1silverhawk]

Without the heat riser from the manifold, you can remove the hoses and cap off any vac ports they come from.

Yeah, it doesn't have one of those. I'll be sure to plug up the port.

Thanks!