A new (in the box) plastic gas tank was with my 54 F100 when I bought it. It is from a company called Tanks. It fit fine in the original location. I plumbed it with steel NAPA brake lines to the 223 six.. The new sending unit came with good directions and went in with out any problem. There is a tapping for a vent. Should I plug it or use it? If I use it, where should it be run to? What kind of fitting should be at the end of the line?
Thanks
Bob

 

bump. trying again

 

My thinking is that if the original tank did not need a vent, you don't need one either.
The vent might be necessary for fuel injection with supply and return lines that could cause the tank to see a little pressure build up. Or for later model evaporative emission applications where vapors are returned to the tank.

 

I used a roll over vent to a hose outside the cab. This way you can use a non vented cap to keep the fumes down.

 

I'd use the vent. The roll-over vent rhopper mentioned has a marble that seals the vent if the truck turns upside down, to prevent spillage and possible fire. The probability of needing that is pretty slim, imho. (let's hope we never do, anyway) A rubber hose looped up into the frame rail will do fine. Having an external vent will make filling the tank easier at the gas station, allowing a place for the air in the tank to escape to as the fuel goes in and displaces it. If you don't have a vent, all that air has to come back up the filler neck at the same time the gas is going in. That can get messy if it burps.

 

I am using the original tank in my 56 with a vented cap. Never smelled any fumes or had a problem with it "burping".

 

I used the rollover valve/vent, and a non-vented cap

Sam

 

Thanks guys. So it's my option. Either way works.

 

I had fume smell inhe closed shop before the vent valve with s vented cap. Do not have it now

Sam

 

Hi Guys,
I went round & round with the guys helping me with this build.
Their argument was that they had been racing dirt track for 20 years & they don't require rollover valves so why put one on this big 'ol truck.
My argument back was my garage faces west it's hot as he-- in there & I have a water heater with a lit pilot light in a closet in the garage. I don't want to take any chances...

The valve is only $10 - why not put one in?

Ben in Austin

 

These old trucks had a filler pipe that was big, unobstructed, and almost 2 inches in diameter. Modern filler pipes have a small hole, just big enough for the pump nozzle to fit so these need an air by pass. The old big filler pipe needs no bypass since there is plenty of room to let the air from the tank vent out. All the tractors and machinery on our farm had similar, big filler pipes and unvented caps. I would presume that venting would not be necessary if a large stock type filler pipe is used. This is only my opinion though.

 

Aren't vented caps designed to let air in and not out? I seem to remember the slight hissing sound opening the gas cap on hot days, yet the truck never stopped running because vacuum built up as fuel left the tank.

 

Next time I'm at the auto parts store I have to pick up a vented cap. I have a non vented cap on it now and it built up a lot of pressure, which I didn't realize until I was working on something under the hood and took one of my fuel lines off... squirted gas all over. Scratched my head, and then took the gas cap off and heard the pressure release.... Original tank.

 

I have heard, but not seen any of those valved caps.

the mustang cap I used temporarily for the green tank and mustang tank and filler neck, had a little groove in the sealing edge.. that was the vent.. both in and out.
these were all stock parts.

I replaced the filler neck with a tube & cap from a late model silverado (short, straight, screw in cap.) it is NOT vented... so I had to add something else..

this is NOT about speed to fill the tank, this is about the tank sitting with fuel and the vapors escaping. On the later model vehicles this goes thru a charcoal canister to capture the released material.

Sam

 

I'm not discouraging the use of the rollover vent. Safety is a good thing. But to be clear, that valve will do nothing for sealing fumes from your hot garage and away from your gas water heater. The valve only closes if it's tipped upside down. Otherwise, it's a normal, open vent.