47-55.1 Filler neck question

[51 3600]

I'm using the stock AD filler neck connected to a rear mounted tank exiting at the top back of the driver rear fender. Is a stock gas cap vented? I ask because I'm assuming the vent hose from the tank to the filler neck is adequate for venting so I don't need to use the available barbed vent fitting on the tank. (Disregard the position of the hose clamps. They're looses at the moment.)

[Hcb3200]

Unless that tank has another route to ambient air. such as thru a charcoal cannister or another vent location. Then the gas cap should be vented.. Most Stock caps were vented

[dsraven]

Pretty sure the original cop is vented. You could put a little pressure in the tank through a fuel line and see if it vents I guess.
What will your actual filler height be? I ask cuz if it's low you could have filling issues or a full tank may slosh around enough to cause the cap to be damp or actually wet with fuel.

[mr48chev]

The original caps are and have to be vented. That "vent hose" is to let air out of the tank faster when you fill the tank without it trying to push past the gas in the filler neck. It isn't tO vent the tank with the cap on.

I like the idea of using a stock filler neck rubber gromet around the filler neck in the fender to give it an it was there to begin with look if you don't put a gas door in the fender .

You could put a T in that line and run a vent line over and up though the stake pocket to vent the tank and have a non vented cap or not have to worry that you did or didn't have a vented cap. The primary reason for venting the tank is to let air in to replace the gas the fuel pump pull out or the fuel pump creates a vacuum in the tank that it finally cannot overcvome and the engine quits.

[Hcb3200]

I agree with a T in the line. but I would add a charcoal cannister to that vent line. This way does not stink up that nice garage. And agree with Mr48 nothing like "leaving your cap somewhere" and the replacement is not vented. ask me how I know.

[mr48chev]

I went through three Stant caps on my 51 Merc that had the correct number on the box for a vented cap but were not vented before I got a cap that was vented. The first time I walked a mile to a gas station and back to get gas because I though I was out and then the car stalled on the same corner the next morning on the way to work again. That time I went to open the cap to put the gas I had in the jug in the trunk in the tank and heard the bottom of the tank pop back out when air got in the tank.

Agreed on the charcoal canister thing, it doesn't take a lot of effort or expense to run a vent line to the engine compartment where you have the canister

[leegreen]

That vent hose is also a drain. Those filler necks have an inner and outer chamber so that if a small amount of gas spills from filler neck it drains back to tank.

51-3600 - I'd go on the back of the fender not top. Mine is on top, it presents two issues. Old time chrome gas caps with key locks will let rain through the key hole into the tank. Any slop when filling up goes all over the fender and stains the paint.

Do you have a part number for the 90 bend filler hose you used? My setup is similar but needs a better vent and I like your hose better than what I used.

I used an original AD style rubber grommet where filler goes through fender as mr48chev suggested - it worked out well.

If I redo things I'll think hard about a filler door in fender, more work but solves some of the other issues

[51 3600]

90 degree bend is from Tanks Inc. 1 1/2" ID, part # NE-90-1.5
Thanks all for the info. Guess I'll use the vent line off the tank and run a hose to a rollover valve and charcoal canister. Like said, canister a good idea to keep fumes out of garage.

[Hcb3200]

put a T in the filler neck vent hose run a loop up inside the fender up and higher than cap if possible then take that loop down and under to charcoal canister. you still need the line for the filler neck and it keeps that functioning as it should.
up and above or at least to cap level keep sloshing outside of the cannister tube line. you can put the cannister under the bed. and not have to run it up to the engine bay like all modern trucks these days. Put your rollover on the exist port of the charcoal cannister. because if it rolls the canister will the last thing you need to worry about.

[51 3600]

Thanks Hcb3200, I'll look into doing that.

[dsraven]

if you have fill issues with the current set up, like the pic, possibly turn the filler so the vent pipe isn't on the bottom side. that way venting air won't be blowing past the fuel that is incoming. stock would have that vent pipe located on the 3/9 position on the filler neck.
nice clean work you do. nice.

[mr48chev]

I think most standard nozzles will reach down past that vent tube but it might be an issue filling it out of a jug.

[dsraven]

true. i always think worst case scenario. sorry boys.

[51 3600]

No fill issues yet...but then the truck's not ready to run yet so I've never put gas in the tank.
In case some are unaware: as you can see in the pic below, the actual filler neck is inside the whole assembly. It is about 1 1/4" in diameter whereas the exterior portion is about 2 1/4" in diameter. The vent tube opens into the space between the inner and outer neck. So when filling at the pump or with a gas can and funnel, no fuel is able to enter the vent tube. Pouring from a jug as mr48chev suggests could cause fuel to enter the vent tube.



Another pic just to show where the filler neck is mounted on the fender. The 3 "stars" show where mounting studs attach on the underside of the fender. The 3 wings on the filler neck attach to those studs.

Edit: I don't know how the neck image was duplicated and my thread starting image ended up here. First for me.

[mr48chev]

That is going to look like a factory install when you are done.

I forgot about that tube inside the filler neck as my 48 came with the tank under the right side of the bed but the 54 that I learned to drive in in when I was 12 had that tube. The whole Idea being that when you fill the tank it doesn't burp gas back on you if you have a fast fill pump. They are a lot faster now than they were in 1954 too.

40/41 Ford pickups had the filler right about in the same spot for the world to see along with their coupes and sedans having them there.