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1977 Need Emission Guidance

Bad news on the original documentation angle...

Seems my K5 was made in "Plant F" and no records exist from that plant.

Grrrrr, back to square one. I may just puts Cats on it,. Would that create much back pressure or enough that it would effect engine operation?

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I do not believe GM ever put dual cats on trucks. At least not that vintage. Adding or subtracting cats from original is federally illegal, but there is not much federal enforcement I'm aware of. The state is all you have to worry about IMO.

Modern converters are not a restriction. They haven't been for a long time. It was the old pancake style that GM used which sucked for flow and got worse as time went on.

There is a bit of science to installing converters (placement to get the inlet temps correct), I assume that is part of why the feds made it illegal to change the number, but part of it is probably just stupid bureaucracy.

Single 3" pipe will support a fair bit of HP. Single has a lot of benefit to it, but I know some folks like the way duals look.
 
dyeager535 said:
I do not believe GM ever put dual cats on trucks. At least not that vintage. Adding or subtracting cats from original is federally illegal, but there is not much federal enforcement I'm aware of. The state is all you have to worry about IMO.

Modern converters are not a restriction. They haven't been for a long time. It was the old pancake style that GM used which sucked for flow and got worse as time went on.

There is a bit of science to installing converters (placement to get the inlet temps correct), I assume that is part of why the feds made it illegal to change the number, but part of it is probably just stupid bureaucracy.

Single 3" pipe will support a fair bit of HP. Single has a lot of benefit to it, but I know some folks like the way duals look.
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The truck has headders on it and an exhaust system that needs to be replaced. There is an obvious leak that needs to be fixed. I am going with DUAL mufflers that exit out the back of the truck. I will put the cats as close to the headders that is reasonable but will need to decide that with the muffler shop.

OR

I am going to register the truck as a collectible which will exempt me from emissions testing. I will only have to pass an "enhanced" safety inspection. I am still trying to figure out what that means.

I am going to have to lower it

Remove 4" suspension lift and add 2" suspension lift
Remove 40" tires and replace with 35" tires and different rims

Hopefully that lowers the bumpers to the legal height of 29" in rear and 27" in the front. RIGHT NOW it is 33" in the front and 35" in the rear.

I also need to remove a horribly rusted driver side door sill. Just go a new welder and one of the first things I need to do is weld in a new section of metal.

Fun!!!!
 
My 77 3/4 ton burb oem smb 400, t350, np203. had only an AIR system. smogged in kommiefornia many times that way.
 
Wes Harden said:
My 77 3/4 ton burb oem smb 400, t350, np203. had only an AIR system. smogged in kommiefornia many times that way.
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3/4 tons often had less emissions than the 1/2 tons.
My 84 3/4 ton was normal carb the 84 k5 was a nightmare ccc carb and esc dizzy.
 
Capt Ron said:
Sorry but I have to disagree, my 77 has the factory RPO sheet in the glove box and it shows factory dual exhaust. I believe there is no way the factory put dual cats on anything in 1977 except maybe Corvettes. Also there are only heat shields where the mufflers are located, if it had cats there would be another set of heat shields.
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I agree. I have a 77 Jimmy that has the factory 400. No cats and I'm in California. You will have to have EGR, smog pump, exhaust manifolds with AIR tubes and a canister. No Cats because of HD emissions. I just passed smog after a rebuild and a replacement of a bunch of the fuel lines coming from the tank. Apparently after 40 some odd years, they fall apart. I also passed the sniff test with 2.02 heads.

edit. Also must have the heat stove pipe going from the passenger exhaust manifold to the air cleaner. Smog guy was VERY adamant about that.
 
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Joel Wilson said:
I agree. I have a 77 Jimmy that has the factory 400. No cats and I'm in California. You will have to have EGR, smog pump, exhaust manifolds with AIR tubes and a canister. No Cats because of HD emissions. I just passed smog after a rebuild and a replacement of a bunch of the fuel lines coming from the tank. Apparently after 40 some odd years, they fall apart. I also passed the sniff test with 2.02 heads.

edit. Also must have the heat stove pipe going from the passenger exhaust manifold to the air cleaner. Smog guy was VERY adamant about that.
Click to expand...

Did the inspection station question you lack of Cats or EGR? All the stations around me have "know it all" kids working and they won't be persuaded into admitted I'm right about NO CATS on my K5
 
ZombieK5 said:
The truck has headders on it and an exhaust system that needs to be replaced. There is an obvious leak that needs to be fixed. I am going with DUAL mufflers that exit out the back of the truck. I will put the cats as close to the headders that is reasonable but will need to decide that with the muffler shop.

OR

I am going to register the truck as a collectible which will exempt me from emissions testing. I will only have to pass an "enhanced" safety inspection. I am still trying to figure out what that means.

I am going to have to lower it

Remove 4" suspension lift and add 2" suspension lift
Remove 40" tires and replace with 35" tires and different rims

Hopefully that lowers the bumpers to the legal height of 29" in rear and 27" in the front. RIGHT NOW it is 33" in the front and 35" in the rear.

I also need to remove a horribly rusted driver side door sill. Just go a new welder and one of the first things I need to do is weld in a new section of metal.

Fun!!!!
Click to expand...


Well look bud, you'd do yourself a big favor and get it registered as an antique ! I know I sound crazy or an idiot, but your so far off the reservation it would be a nightmare to try and get it registered as a current truck or even a collectible. Skip all that and register it as an antique. Just my $0.02 but I've had my fights with Harrisburg. As a antique, your not held down to a particular emissions critique or standard. And it can still be operated on public roads, but it still needs to conform to the mechanical safety standard in effect today.
 
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Joel Wilson said:
must have the heat stove pipe going from the passenger exhaust manifold to the air cleaner. Smog guy was VERY adamant about that.
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Yep, just one of the first things people remove and a smog Tech in California could lose their license if they miss it. Granted, that stove pipe is only for winter cold starts which we don't really have in California, they still check it anyways.
 
Killain said:
Well look bud, you'd do yourself a big favor and get it registered as an antique ! I know I sound crazy or an idiot, but your so far off the reservation it would be a nightmare to try and get it registered as a current truck or even a collectible. Skip all that and register it as an antique. Just my $0.02 but I've had my fights with Harrisburg. As a antique, your not held down to a particular emissions critique or standard. And it can still be operated on public roads, but it still needs to conform to the mechanical safety standard in effect today.
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My issue is my K5 is not "substantially in conformity with manufacture specifications" so collectible is my only avenue unless i find an inspection station that is enlightened.

Problem with collectible is I will need to have it in "show" condition, whatever that means.

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Well I have a hard time thinking you'll be able to establish it as a "collectible". It is pretty modified and I don't know it can be returned in it's present condition ? Have you contacted any other dirt track owners ? What did they do to be able to operate on the street ?
 
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ZombieK5 said:
Did the inspection station question you lack of Cats or EGR? All the stations around me have "know it all" kids working and they won't be persuaded into admitted I'm right about NO CATS on my K5
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I forgot to add that you will need an EGR, even though it's that funny detached EGR thing. Which is kinda nice since you can add pretty much whatever intake you want. We are the 2nd owner of this Jimmy and when we bought it, it had the original exhaust with no cats. I put dual exhaust with 24" glasspacks on it and have never had a problem getting it passed. Few fix it things here and there, but always eventually passed.
 
Joel Wilson said:
I forgot to add that you will need an EGR, even though it's that funny detached EGR thing. Which is kinda nice since you can add pretty much whatever intake you want. We are the 2nd owner of this Jimmy and when we bought it, it had the original exhaust with no cats. I put dual exhaust with 24" glasspacks on it and have never had a problem getting it passed. Few fix it things here and there, but always eventually passed.
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The factory manual for my model year showed that the 400 cubic inch small block Chevy did not have an EGR valve. Most of those were limited to California vehicles and the 350 cubic inch and Below engines.

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Killain said:
Well I have a hard time thinking you'll be able to establish it as a "collectible". It is pretty modified and I don't know it can be returned in it's present condition ? Have you contacted any other dirt track owners ? What id they do to be able to operate on the street ?
Click to expand...

It seems that the magic of the collectible designation is that the vehicle can be highly modified. The only issue is that it has to be in some type of show condition. I am in the process of getting it to that point.
 
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