The Stovebolt Site Forums The Shop Area General Truck Talk 1956 3100 Task Force Non Vented Gas Cap

I just installed a Vapor Trapper charcoal canister (https://www.vaportrapper.com/) above the tank and vented through the floor outside. This was done to reduce or eliminate the gas smell in the garage. Instructions state that the gas cap must be non vented, which makes sense to force fumes through the canister. I can find non vented caps for the sedans but having trouble with one for a truck.

I am hoping someone here has information on an exterior non vented cap for the truck. or able to point me towards a resource that can assist.

Thanks, Joe

Try looking up stant gas cap fitment guide they may have some application that may work or if your local flaps have some stock you can bring the old cap down and match up the ears to fit on your truck and you can see if the caps they have are vented .

There might be some out there that fit but vented caps were the only type auto makers were using back then as it was the only way to vent the tank and allow fresh air inside to replace fuel as it was pumped out.

Is it possible to modify the vented cap to block the vent hole?

All of the caps that I have bought from Classicparts.com for AD trucks are essentially non-vented. They cause a vacuum in the tank as gas is removed, as well as cause pressure inside the tank on a hot day.
I don't know if they fit Task Force trucks. They probably do.
If they don't fit, I would be surprised if the ones they sell for Task Force trucks were not also essentially non-vented.

Yes, Carl you're right. They are vented caps but the valve that vents the cap fails frequently. He'd probably buy one that actually worked.

The part number for the TF and AD truck caps is the same so he'll have to find a cap with the same locking ears that isn't vented. You're probably going to have to dig through boxes of gas caps to find one. Unfortunately parts stores don't carry a lot of these style caps anymore. They're all modern plastic ones.

Here's what the AD , TF gas cap looks like. The vents could probably be epoxied shut.

Thanks gents, I will try the epoxy idea. Joe

Got mine from the local napa it had one that was non vented.
I did the charcoal cannister as well.

Here’s what I have on the 72 c30 after I misplaced the one on it. Per advance auto computer. The old one never built up pressure in the tank. The new one built up pressure in the tank. I took a 1/8 drill bit and ran it down the 5 holes on the new cap solved the pressure problem.

I have the same one. I bent those tangs and took it apart, removing the valve and spring inside. No more problems. Interestingly it worked fine for a couple years then suddenly I had a negative pressure situation in the tank.