[V8&4spd]

You have a 750 cfm carb. You might be able to use a 800 cfm carb. I don't know how that will affect any smog testing.

[lt1silverhawk]

Originally Posted by V8&4spd

You have a 750 cfm carb. You might be able to use a 800 cfm carb. I don't know how that will affect any smog testing.

Good point. I guess I can swap carbs while doing the intake. I think 750 is enough, since either one only delivers what the engine demands. And I did paint mine oh so purty lol!

[75gmck25]

Make sure you are using the right emissions diagram for the model of your truck.

What is the GVWR of your truck (its on the data plate inside the driver's door). Its probably a 1/2 ton with standard emissions, but if its a 3/4 ton with a GVWR over about 8000 lbs the emissions may be different. Make sure you are using the right emissions diagram for your truck.

My '75 is a camper special with 8200 GVWR, and the factory emissions are fairly simple. All I have is a fuel vapor recovery tank, with no EGR and no catalytic converters from the factory.

Bruce

[cobalt327]

Originally Posted by 75gmck25

Make sure you are using the right emissions diagram for the model of your truck.

What is the GVWR of your truck (its on the data plate inside the driver's door). Its probably a 1/2 ton with standard emissions, but if its a 3/4 ton with a GVWR over about 8000 lbs the emissions may be different. Make sure you are using the right emissions diagram for your truck.

My '75 is a camper special with 8200 GVWR, and the factory emissions are fairly simple. All I have is a fuel vapor recovery tank, with no EGR and no catalytic converters from the factory.

Bruce

I barked up this tree, too. Thanks for the reaffirmation.

I recall this being a C20, I think. So it's more than a 1/2 ton. How much more would be what I would want to know.

[lt1silverhawk]

Originally Posted by 75gmck25

Make sure you are using the right emissions diagram for the model of your truck.

What is the GVWR of your truck (its on the data plate inside the driver's door). Its probably a 1/2 ton with standard emissions, but if its a 3/4 ton with a GVWR over about 8000 lbs the emissions may be different. Make sure you are using the right emissions diagram for your truck.

Originally Posted by cobalt327

I barked up this tree, too. Thanks for the reaffirmation.

I recall this being a C20, I think. So it's more than a 1/2 ton. How much more would be what I would want to know.

My apologies guys. Actually, there are two threads related to this truck (click here for the other one), and I tried my best to keep the two separate, with this one focusing simply on the carburetor's rebuild and the other one dealing with the truck's specific problems. But this thread has now gone beyond that and both threads are being updated daily so I sometimes get mixed up about what I may have posted where. I swear I'm not trying to make this into a "guess my emissions setup" contest lol!

I posted in the other thread that the truck does not have the emissions label under the hood, and also linked to a set of diagrams from Chilton's online that are essentially the same as what V8&4spd posted earlier.

I went to look for the data plate but did not find one. Below is what I did find. The blocked out portion is the vehicle's VIN. Does this provide any info?






As always, thank you for the continued help

[cobalt327]

I tried a search for "YF5 emissions", etc. and got basically nowhere.

I recall the smog station telling you it needed an EGR. My only question about this is, because all the other emissions devices were left intact, why would the PO then do something as obvious as removing the EGR if it was there in the first place?

The difference in the cost of the intake w/ and w/o the EGR isn't much. It's VERY obvious to a visual inspector that it's missing- so if it needs one, how was it passing CA emissions previously?

But- would it surprise me to find out it needed one? No- CA has traditionally had the strictest emissions in the country.

[lt1silverhawk]

Originally Posted by cobalt327

I tried a search for "YF5 emissions", etc. and got basically nowhere.

I recall the smog station telling you it needed an EGR. My only question about this is, because all the other emissions devices were left intact, why would the PO then do something as obvious as removing the EGR if it was there in the first place?

The difference in the cost of the intake w/ and w/o the EGR isn't much. It's VERY obvious to a visual inspector that it's missing- so if it needs one, how was it passing CA emissions previously?

In retrospect, the smog tech was more concerned about the visual inspection (required to pass) than actually smogging the vehicle. I did ask him for a "pre-test" to see what the numbers were like, but he wouldn't do it, saying that the C.A.R.B. boys were really cracking down hard on all shops.

As to how to passed smog before, either the vehicle's emissions are good and some shop went ahead and smogged it without worrying about the visual inspection. Or it passed illegally.

I got in touch with the previous owner about the smog a while back and he said the ower before him had smogged the truck before selling it to him. And although the seller is required by CA law to smog the vehicle before selling it, I didn't have him do it because of the way the final price was worked out. He had also mentioned that the truck had passed smog "recently".

Here's what's throwing me off: there is no data plate. Were they not standard on all vehicles at the time? There is just a small plate titled "Assigned Identification Number" with the VIN and a "Control Number". I have never seen one before and have no idea what that means.

Anybody with any input or a helpful direction please do chime in.

[cobalt327]

Does the VIN that's on the plate follow the format shown HERE? If not, the original VIN plate may have been removed, or the vehicle is rebuilt, etc.

Is there a spot on the dash driver side w/2 holes where the original VIN tag would have been riveted?

[V8&4spd]

You have a assigned title. That is not the VIN that came on the truck. The truck might have been made from other parts or something happened to the VIN. If the truck came from out of state it might not have had the CA smog equipment on it.

[lt1silverhawk]

Originally Posted by cobalt327

Does the VIN that's on the plate follow the format shown HERE? If not, the original VIN plate may have been removed, or the vehicle is rebuilt, etc.

Is there a spot on the dash driver side w/2 holes where the original VIN tag would have been riveted?

I'll have to verify the exact VIN once I get home, but Im 100% sure that is the format, and includes the letters CLK in the first part. I did see the rivets behind the plate this morning.

Originally Posted by V8&4spd

You have a assigned title. That is not the VIN that came on the truck. The truck might have been made from other parts or something happened to the VIN. If the truck came from out of state it might not have had the CA smog equipment on it.

That, or the vehicle was perhaps retrofitted with the standard VIN later on?

California DMV site was of no help. However, according to DMV.org:

1981 was a pivotal year for vehicles. That year, the National Highway Traffic Safety Administration (NHTSA) required all vehicles to have a standard, 17-character vehicle identification number, or VIN. Since then, automakers all over the world have adopted the VIN.

Apparently the issue has come up on this forum before, but nothing was found.

[Bullsnipe]

Hi, I am a former California Smog Tech. I moved from the Left Coast in 1998 so I have been out of the loop for some time. I understand the Tech not wanting to "Pretest" We were required to scan the barcode on our license before we could start the test. We were required to manually exercise the EGR valve and note a drop in RPM. I know that 12 years ago that behind closed doors the test could be faked. You test a good vehicle but enter the data for the vehicle you want the cert for. We had manuals that specified all the smog equipment that was required. When in doubt, the customer would have to take his vehicle to a Cal Referee.

[cobalt327]

Originally Posted by lt1silverhawk

I did see the rivets behind the plate this morning.

What I was wondering was, is the VIN plate missing from the dash where I would expect it to be (leaving 2 holes in the dash), and that the tag you now have was a "replacement" for whatever reason? Or is this tag in that dash location now?

Because there should be a manufacturer-attached VIN tag, not just a tag from CA, unless this truck has had considerable repair work or repair that would encompass replacing the original dashboard assembly, or it's a resurrecting junked or "rebuildable" vehicle, or whatever.

[75gmck25]

My truck (which is a '75 GMC) has a data plate riveted to the door frame, just below the striker post on the driver's side door frame. This plate has the VIN number, and it also lists GVWR (8400 lbs for my truck), and the front and rear axle weight ratings. This is supposed to be the stock data plate location for 73-78 GM trucks. Have you tried looking for a data plate in that location?

This URL shows a picture of a similar data plate (mine is a little different) http://www.chuckschevytruckpages.com/VINIDPLT.html

Bruce

[cobalt327]

Originally Posted by Bullsnipe

Hi, I am a former California Smog Tech. I moved from the Left Coast in 1998 so I have been out of the loop for some time. I understand the Tech not wanting to "Pretest" We were required to scan the barcode on our license before we could start the test. We were required to manually exercise the EGR valve and note a drop in RPM. I know that 12 years ago that behind closed doors the test could be faked. You test a good vehicle but enter the data for the vehicle you want the cert for. We had manuals that specified all the smog equipment that was required. When in doubt, the customer would have to take his vehicle to a Cal Referee.

Thanks for stopping by. I recall the original poster to this thread saying the shop he took it to said the truck needed the EGR. My concern was that the vehicle may have been exempt from some emissions requirements/equipment due to the GVW, because the all emissions equipment appears to have been retained on this truck other than it not having an EGR valve on the aftermarket replacement intake.

Do you know if ALL CA trucks (C20 in this case, w/350 SBC) had to have an EGR, or if any trucks in CA were exempt like they could be in other areas of the country?

[lt1silverhawk]

Hey Bullsnipe,

Originally Posted by Bullsnipe

Hi, I am a former California Smog Tech. I moved from the Left Coast in 1998 so I have been out of the loop for some time. I understand the Tech not wanting to "Pretest" We were required to scan the barcode on our license before we could start the test. We were required to manually exercise the EGR valve and note a drop in RPM. I know that 12 years ago that behind closed doors the test could be faked. You test a good vehicle but enter the data for the vehicle you want the cert for. We had manuals that specified all the smog equipment that was required. When in doubt, the customer would have to take his vehicle to a Cal Referee.

The tech took one look under the hood and, after realizing that there was no EGR, pulled out a thick book and looked up my truck. I'm not sure under which specific model he searched (C/K 10/20 etc) but for the 350 engine, he said there should be an EGR. I took his word as final answer because I've known him for so long, and he seemed dead set against testing my truck. But now I believe it is a good idea to try another shop. Not sure who the refs are but I'll ask.

As to the pretest, it is advertised at their shop as an available service in case the owner thinks the vehicle might fail. Kind of like a practice test I suppose to see where someone is weak at. Then again, as jaded as the tech has become, he could've just been having one of those days.

Thanks, I appreciate the tips and info Bullsnipe! And welcome to the site!

Originally Posted by cobalt327

What I was wondering was, is the VIN plate missing from the dash where I would expect it to be (leaving 2 holes in the dash), and that the tag you now have was a "replacement" for whatever reason? Or is this tag in that dash location now?

Because there should be a manufacturer-attached VIN tag, not just a tag from CA, unless this truck has had considerable repair work or repair that would encompass replacing the original dashboard assembly, or it's a resurrecting junked or "rebuildable" vehicle, or whatever.

Originally Posted by 75gmck25

My truck (which is a '75 GMC) has a data plate riveted to the door frame, just below the striker post on the driver's side door frame. This plate has the VIN number, and it also lists GVWR (8400 lbs for my truck), and the front and rear axle weight ratings. This is supposed to be the stock data plate location for 73-78 GM trucks. Have you tried looking for a data plate in that location?

This URL shows a picture of a similar data plate (mine is a little different) http://www.chuckschevytruckpages.com/VINIDPLT.html

Bruce

Sorry cobalt327 and Bruce, long day today. There is no VIN on the dash, nor any holes where it should be at. Instead of the data plate, the "Assigned Identification Plate" is riveted to the driver-side door frame below the door striker. Aside from the sticker I posted, I was unable to find any type of tag from the manufacturer. If the truck had been extensively repaired, wouldn't it be titled as salvaged (it isn't).

Originally Posted by cobalt327

Does the VIN that's on the plate follow the format shown HERE? If not, the original VIN plate may have been removed, or the vehicle is rebuilt, etc.

The VIN on the plate does follow that format and it comes out as a Light Duty Chevrolet Conventional Cab 4x4, 350 165 HP 4 bbl, 3/4 ton, Cab and Pickup Box or Van with Hi-Cube.

Going by this page, if I go by the RPO codes on the sticker(provided mine are correct), the 4.56 ratio rear axle, a a 350 V8, and TH400 were offered with 4wd in the K20.