Vapor canister

[K10-Kansas]

Hi all. I the previous owner removed the vapor canister and nearly all the lines. Will a vapor canister help with gas smell? Will this vapor canister work for a 71 with a new carbureted 350? Where can I find more info or putting in lines? Thanks in advanced for any help on this

[howzzzit]

The lines and routing should be in the assembly manual. Are you using the eec gas tank? If so, they use a non vented cap. There is a vapor line that goes up inside the cab behind the door. Makes an upside down loop and the goes to the vapor canister. The charcoal is suppose to absorb gas odors. This is your gas tank vent. I'm assuming the loop is to prevent liquid. That canister looks like mine on my 72. Nothing magical about them.

[HO455]

Yes the vapor canister will help, if not solve the gas fume smell.

[Accelo]

If it is missing I wounder if and of the hoses in the interior of the cab are disconnected. You didn't mention if the smell is inside or outside. Same possibly the lines under the hood, did they plug them after the removal?

[howzzzit]

See post #7

https://67-72chevytrucks.com/vboard/...d.php?t=601940

[dmjlambert]

I have a 1969 truck parked in the garage, and it did not come with a vapor canister and there is no significant gas smell. It may be because I have a gas tank with no open vent lines, and a vented gas cap. I suggest look at your tank and make sure the vent lines are not just cut off, that they are plugged completely, and that your fuel sender rubber gasket is newish with no cracks, and your gas cap should be the vented type. A vented gas cap is completely sealed but it will let air pass in or out over a certain small amount of pressure or vacuum, although some people drill a small hole in a non-vented cap and call it vented. You need to fully check out what the previous owner has done.

With that said a vapor canister may be a good idea to reduce the smell and reduce emissions and I am considering adding one. I believe the stock vapor canister is not reproduced at all, and unless you are going to replace the activated charcoal in a used one you are probably better off using one like in your first post. But the only ones with a purge valve built into the canister are the original ones that are not reproduced. I have seen many used ones listed (or maybe it is same one listed over and over) that have obviously busted purge valves on top. And if you get one with no obvious signs of broken purge valve it is very possible the purge valve is not working on a 50 year old canister. If I were to add a canister, I would get a new canister as in the picture you show, and add a new external purge valve. An external purge valve can be replaced separately if you should have a problem with it.

[MARKDTN]

A charcoal canister is a good thing and does not reduce performance. I have used several from 88-95 TBI trucks on various EFI projects. They have 2 lines; 1 to tank and 1 to a canister purge valve. On a carbureted application it might be more difficult.

[71CHEVYSHORTBED402]

Info. for my 71 402 with a factory Rochester. Strikes me a 350 would be the same. Be nice to know if that cannister fits and works, so far I'm unaware of a replacement.

The vapor canister bracket mounts using the bolts for assembling the RH gusset to the fender.

The vapor canister belt secures the canister to the bracket using two 7/16" hex recessed head bolts with spin washers. The bolt threads are 1/4-20 x 1/2”, and the heads are stamped “S”. The canister’s ports face the rear.

The vapor canister hose connections are:

• A 1/4” ID fuel (PCV/EEC) hose connects to the canister’s “PCV” port with a pinch clamp, and to the vacuum tee in the PCV valve hose. The tee reduces the 3/8” PCV hose to 1/4”.

• A 5/32” ID vacuum hose connects to the canister’s CARB port with a pinch clamp, and to the carburetor’s vacuum port above the fuel filter fitting.

• A 5/16” ID fuel vapor (PCV/EEC) hose connects the canister’s TANK port to the lower vent tube with pinch clamps.

A black nylon strap secures the 1/4” and 5/32” vapor hoses to the A/C muffler assembly’s front line. The hoses route behind the compressor’s upper flange to the vapor canister. This strap secures the A/C compressor wire as well.

[K10-Kansas]

Originally Posted by howzzzit

The lines and routing should be in the assembly manual. Are you using the eec gas tank? If so, they use a non vented cap. There is a vapor line that goes up inside the cab behind the door. Makes an upside down loop and the goes to the vapor canister. The charcoal is suppose to absorb gas odors. This is your gas tank vent. I'm assuming the loop is to prevent liquid. That canister looks like mine on my 72. Nothing magical about them.

Great. I'll check the manual. Yup, i have an eec gas tank.

[K10-Kansas]

Originally Posted by Accelo

If it is missing I wounder if and of the hoses in the interior of the cab are disconnected. You didn't mention if the smell is inside or outside. Same possibly the lines under the hood, did they plug them after the removal?

The line was cut just under the cab. So the part missing is the line below the cab running to the canister, canister is missing, and the line to the carburetor. I see there are 3 ports on the canister in the picture so not sure where the 3rd one goes. Maybe a to vacuum?

[Rich72C10]

Yes, one line from the canister goes to the carb. When I got mine all done, all the gas small was gone in my garage. It was well worth getting it operational.

Number of threads about this on the board and blogs on the internet. I still even have a bracket for sell. When looking for a canister on eBay/internet, be sure to look outside of our trucks. For example a canister I got was listed for a Vette.

Here is a thread on the forums that I posted on, could be helpful to you.
More vapor canister stuff - Cut one open and observations.

[K10-Kansas]

Originally Posted by howzzzit

See post #7

https://67-72chevytrucks.com/vboard/...d.php?t=601940

Thanks. I appreciate the pictures.

[K10-Kansas]

Originally Posted by dmjlambert

I have a 1969 truck parked in the garage, and it did not come with a vapor canister and there is no significant gas smell. It may be because I have a gas tank with no open vent lines, and a vented gas cap. I suggest look at your tank and make sure the vent lines are not just cut off, that they are plugged completely, and that your fuel sender rubber gasket is newish with no cracks, and your gas cap should be the vented type. A vented gas cap is completely sealed but it will let air pass in or out over a certain small amount of pressure or vacuum, although some people drill a small hole in a non-vented cap and call it vented. You need to fully check out what the previous owner has done.

With that said a vapor canister may be a good idea to reduce the smell and reduce emissions and I am considering adding one. I believe the stock vapor canister is not reproduced at all, and unless you are going to replace the activated charcoal in a used one you are probably better off using one like in your first post. But the only ones with a purge valve built into the canister are the original ones that are not reproduced. I have seen many used ones listed (or maybe it is same one listed over and over) that have obviously busted purge valves on top. And if you get one with no obvious signs of broken purge valve it is very possible the purge valve is not working on a 50 year old canister. If I were to add a canister, I would get a new canister as in the picture you show, and add a new external purge valve. An external purge valve can be replaced separately if you should have a problem with it.

I replaced the gas cap when I bought it because the rubber seal inside the old gas cap was dry and cracked. Its an eec non-vented. Thanks for the tip on the rubber seal on the sending unit. I'll pull that off and look at it.

[K10-Kansas]

Originally Posted by 71CHEVYSHORTBED402

Info. for my 71 402 with a factory Rochester. Strikes me a 350 would be the same. Be nice to know if that cannister fits and works, so far I'm unaware of a replacement.

The vapor canister bracket mounts using the bolts for assembling the RH gusset to the fender.

The vapor canister belt secures the canister to the bracket using two 7/16" hex recessed head bolts with spin washers. The bolt threads are 1/4-20 x 1/2”, and the heads are stamped “S”. The canister’s ports face the rear.

The vapor canister hose connections are:

• A 1/4” ID fuel (PCV/EEC) hose connects to the canister’s “PCV” port with a pinch clamp, and to the vacuum tee in the PCV valve hose. The tee reduces the 3/8” PCV hose to 1/4”.

• A 5/32” ID vacuum hose connects to the canister’s CARB port with a pinch clamp, and to the carburetor’s vacuum port above the fuel filter fitting.

• A 5/16” ID fuel vapor (PCV/EEC) hose connects the canister’s TANK port to the lower vent tube with pinch clamps.

A black nylon strap secures the 1/4” and 5/32” vapor hoses to the A/C muffler assembly’s front line. The hoses route behind the compressor’s upper flange to the vapor canister. This strap secures the A/C compressor wire as well.

Thanks a ton for this info. I think I can go ahead and get started on my setup with this.

[71CHEVYSHORTBED402]

Originally Posted by K10-Kansas

Thanks a ton for this info. I think I can go ahead and get started on my setup with this.

You might save thanks until after you buy that 1/4" hose Sure you can install a cheaper one, but IMO it wouldn't be right.

I have instructions for the assembly from the fuel tank if needed, but sounds like you're well on your way. The compartment kinda' looks like this.

[K10-Kansas]

Originally Posted by 71CHEVYSHORTBED402

You might save thanks until after you buy that 1/4" hose Sure you can install a cheaper one, but IMO it wouldn't be right.

I have instructions for the assembly from the fuel tank if needed, but sounds like you're well on your way. The compartment kinda' looks like this.

Well the more info you have to share, the better

[54blackhornet]

I need some help ! My 71 C/20 has no EEC stuff at all. No charcoal canister, single line from pump to carb. No loop from tank on passenger side. Truck has never been butchered , pretty much stock. Sticker on door jamb has 12/70 build date. Question ? What gas cap do you use ?

[dmjlambert]

You should be able to use a vented gas cap with that setup. The setup you describe sounds like my 1969 truck.

[Stocker]

^^^ What he said. My '72 K20 is the same.

[Classic Bowties]

Originally Posted by 54blackhornet

I need some help ! My 71 C/20 has no EEC stuff at all. No charcoal canister, single line from pump to carb. No loop from tank on passenger side. Truck has never been butchered , pretty much stock. Sticker on door jamb has 12/70 build date. Question ? What gas cap do you use ?

^ ^ ^ Agreed, and since we get several gas cap style and application questions per month, here are a few cap Id pictures to go with the two above replies that may help you and others searching in the future. Your original 71 C20 non-eec w/o vapor canister would use the vented cap with the shorter, wider two tab style cap mounting flange (see pics). The below GM AC NOS fuel filler cap pictures show both the "Non EEC" vented and 1972 "EEC" pressure vacuum non-vented double ring caps in both deluxe stainless and standard prime-paint as reqd. styles. For anyone searching, we can supply/offer the 72 double ring pressure vacuum/non-vented GM NOS gas caps in both bright stainless or prime-paint versions. Mel
.

[Classic Bowties]

NOS gas cap mounting flange pictures...
.

[71CHEVYSHORTBED402]

A 1970-71 EEC cap differs from a 1972 for what worth. Can't speak for the difference.

I read someplace an EEC cap has a pressure check valve; the cap allows air into the tank as fuel is used, and only releases air when pressure rises above 3-4 PSI. Fuel vapor otherwise expands into the vapor canister.

[54blackhornet]

Can anyone direct me to a source for the non eec cap ? Why is it so hard to locate one ?

[71CHEVYSHORTBED402]

Originally Posted by 54blackhornet

Can anyone direct me to a source for the non eec cap ? Why is it so hard to locate one ?

Original, original replacement or a good replacement?

[54blackhornet]

I just need one that fits properly for non eec tank. Appreciate your help.