Can You Put a 67 Non Vented Tank in a 72

[JoePolo]

A good friend gave me a like new fuel tank from his 67 C10. I was going to swap out the tank in my 72 which is very very cruddy from years of sitting. I bought a new sender with both lines. Differences I see are the additional line at the passenger side top of the tank and the small hose from the neck to the tank. Do I simply need a vented gas cap now for it to make up for the two lines that do not exist??

I know there is the option to buy the right tank, but trying to find an economical solution first. Filler neck grommet needs to be replaced anyways.

[oneshotkyle]

Yes. But it will smell more turning corners and such. You will have plug off evaporator canister

[dmjlambert]

You can probably cap off the vent lines and use a vented cap as a temporary measure. I recommend keeping your old cruddy tank. I wish I had kept mine from my '69 truck, but I got rid of it on the advice of somebody who didn't know or care that it's hard to find good stuff from the Chinese offerings. If you're interested in getting back to using the 72 tank on the 72 truck, empty it then clean it out by taking it to a radiator shop because some of them will do that sort of cleanout, or fill it with a few gallons of vinegar and put some nuts and bolts or gravel or chain in it and swish it around with the help of a friend. Then give it a sealer treatment. There are sealer kits where you pour some stuff in there and coat the inside of your freshly cleaned tank. Then you'll be able to re-connect the vapor/charcoal canister system again and use a non-vented cap again. There are posts here in the forum about fixing the vapor/charcoal canister system so it will work properly. There will most likely be others who are more familiar with the 72 venting system that will chime in with better details.

[PbFut]

A little other info....The 72 C20 and GMC C25 did not have a vented tank or canister, Calif, or Federal.
Keeping the tank a good idea but storage is dangerous unless you clean out very well. Some of the tank sealing products work quite well if you take your time and do not cut corners. The vapors are the issue. Although probably not the best, I filled all 3 of my tanks with water to displace all vapor and gas. Then did the needed mods and repairs, including welds, then did the recommended steps of the sealing product I used. Can't recall brand but final results were the best I could ask for. Also JB weld works great for pin holes. Had a couple on my crappy welds. One of the saddle tanks was so bad I had to cut two access holes to get inside and sand blast. The welds on the hole covers was so so. I cleaned up the seam and placed some JB where I thought questionable for pin holes that may have occurred. Painted and two years later still looks great and holds without a drip. I'm sure the sealer also helped.

[71CHEVYSHORTBED402]

Originally Posted by PbFut

A little other info....The 72 C20 and GMC C25 did not have a vented tank or canister, Calif, or Federal.
Keeping the tank a good idea but storage is dangerous unless you clean out very well. Some of the tank sealing products work quite well if you take your time and do not cut corners. The vapors are the issue. Although probably not the best, I filled all 3 of my tanks with water to displace all vapor and gas. Then did the needed mods and repairs, including welds, then did the recommended steps of the sealing product I used. Can't recall brand but final results were the best I could ask for. Also JB weld works great for pin holes. Had a couple on my crappy welds. One of the saddle tanks was so bad I had to cut two access holes to get inside and sand blast. The welds on the hole covers was so so. I cleaned up the seam and placed some JB where I thought questionable for pin holes that may have occurred. Painted and two years later still looks great and holds without a drip. I'm sure the sealer also helped.

Interesting. I give, why would they install a canister in a C10 but not a C20 when they have the same drivetrains? Perhaps rhetorical.

My 72 C20 didn't have a canister (402/400) but I figured it had been pulled. I did seem to notice the tank differed from my 71 C10, but didn't study it.

[JoePolo]

I ended up getting it in and hooked up. I made the final vent line that used to return to the tank simply drop out through a hole I drilled in the floor of the truck to vent it outside. Other than that all the connections remained the same and I will run a vented cap.

[72c20customcamper]

Originally Posted by 71CHEVYSHORTBED402

Interesting. I give, why would they install a canister in a C10 but not a C20 when they have the same drivetrains? Perhaps rhetorical.

My 72 C20 didn't have a canister (402/400) but I figured it had been pulled. I did seem to notice the tank differed from my 71 C10, but didn't study it.

Federal emission standards . They based it on GVWR nothing to do with drivetrain.

Most muscle cars went from under 400 ci to over 400 again the federal emission standards stated the under 400 ci had to have more emission control devices in place that’s why GM upped the 396 to 402 AMC went from 390 to 401 . Ford and Chrysler did similar

[PbFut]

In 72 the c20 was considered a commercial vehicle in Calif. No smog rule applied. C10 could be licensed passanger. A 3/4 ton suburban was not classified as commercial because of capacity for passengers so smog rules applied. I did not know about the 400 rule but I tend to think that was federal. I bought a 1972 454 LT5 corvette in 78. It had a canister. Can't recall if there was a pump. I don't think federal cars had them as I had a set of headers on it without air injection. Miss that car.

[72c20customcamper]

Originally Posted by PbFut

In 72 the c20 was considered a commercial vehicle in Calif. No smog rule applied. C10 could be licensed passanger. A 3/4 ton suburban was not classified as commercial because of capacity for passengers so smog rules applied. I did not know about the 400 rule but I tend to think that was federal. I bought a 1972 454 LT5 corvette in 78. It had a canister. Can't recall if there was a pump. I don't think federal cars had them as I had a set of headers on it without air injection. Miss that car.

In NY up until a few years ago all pickups had to have commercial plates . Even little Toyota pickups . And you couldn’t use them on the parkways . This got changed with the popularity of trucks .

Over 400 ci had less emission controls in them . I had a 68 AMX with a 343 4spd that had a smog pump . I also had a 1971 401 Javelin 4spd no pump . And few other emission items were not on that car .

[jumpsoffrock]

Originally Posted by 72c20customcamper

. And you couldn’t use them on the parkways .

Wait wut....?

You couldn't drive a truck on a freeway?

[72c20customcamper]

Originally Posted by jumpsoffrock

Wait wut....?

You couldn't drive a truck on a freeway?

No commercial traffic allowed on parkways here . No RVs or trailers either .

[PbFut]

I remember a family vacation tour of US in 1968. 6 weeks in a truck and small camper. Dad drove it right into Manhattan. Cab drivers went nuts. Nothing but a parking ticket down by Staten Island. He tossed in the trash saying we'd never be back. That was a fun and very educational trip for a 10 year old. Sorry way OT.

[MikeB]

I want to do the opposite with my 69. I'm tired of smelling gas fumes in my garage, especially after a drive.

[PbFut]

You should not be smelling gas using either type tank. You likely have a leak or poorly adjusted float in the carb or cap with bad seal or vent.

[mr48chev]

Originally Posted by PbFut

You should not be smelling gas using either type tank. You likely have a leak or poorly adjusted float in the carb or cap with bad seal or vent.

He also could be topping off the tank before he goes home and at times expansion in the tank can cause fumes being vented out a vented cap. I used to have a habit of stopping and filling the tank just before I got to a show so I could get on the road right after leaving the show and often as not you smelled gas standing around the truck.

Still I'd be checking the whole fuel system from tank filler neck to carb to make sure that there wasn't something out of kilter. I've got an ot truck that I need to check because I think the filler neck hose might be bad.

[72c20customcamper]

Originally Posted by mr48chev

He also could be topping off the tank before he goes home and at times expansion in the tank can cause fumes being vented out a vented cap. I used to have a habit of stopping and filling the tank just before I got to a show so I could get on the road right after leaving the show and often as not you smelled gas standing around the truck.

Still I'd be checking the whole fuel system from tank filler neck to carb to make sure that there wasn't something out of kilter. I've got an ot truck that I need to check because I think the filler neck hose might be bad.

Filler neck hose? The 67 thru 72 the filler neck is part of the tank .

Edit : see that your talking about a different truck model

[PbFut]

I'll add that while working in the area of the fill cap on warm afternoon and fairly full tank there is a faint hint of fuel. I am within 18 to 24 inches from the cap. I beleive it is as Mr 48 chevy says. Full tank will have little air to compress and expansion will push some air out the vent. Less full tank the air will have more air to compress and pressure not rise above vent cap spring pressure. Closest gas station is about 6 miles from me so I have at least a 1/2 gallon of air in tank.