Gas tank vent tube question

[RICH MUISE]

So, we had a thread going about the gas tank cap last month that was quite productive. Now I'm not sure I ever had a leak with the gas cap. I'm pretty sure my new one is sealing quite well, but I'm still having gas spew out, but I think it's actually coming out of the vent tube. The gas cap and rubber grommet don't have any residue on them whatsoever, and the gas is actually spewing over the top of license plate. My vent tube is not stock or in the oem routing, the only thing that is consistent is the tube exits in the same place above the license plate that the oem one did.
One reason my tube is different is that my in tank fuel pump mounting plate (on the top of the tank) had a place where a tip-over type vent fitting could be installed, so I just routed a new vent tube around the gas tank flange and then up into the trunk below where it exits.
So now I'm wondering what stops, or is suppose to stop, the gas from entering the vent tube anyway when it's sloshing around? Any thoughts?

[rmk57]

Mine looks original to the car. Looks like 5/16" tube that exits the tank then follows under the rear lip of the trunk, then up the under quarter panel then straight down and exits through the trunk drop off. It looks to be about 5-6 feet in total length. I would say gravity would stop fuel from entering the vent tube, and whatever fuel that would go into it would quickly drain out.

[RICH MUISE]

The way I made mine, it only runs about 6" before it drops down, so if some does slosh up there, it wouldn't get back to the tank. When pressure builds in the tank, I'm guessing it just pushes the gas out to the atmosphere. I guess I need to get under there and reroute it so it doesn't drop down. I guess I need to look at the design of the tip-over vent valve as well. Maybe it's not a good design for our application.

[Ford Blue blood]

The key to the stock vent not "sloshing" is the huge loop up in and under the quarter panel.  That route puts the high point of the vent some 10 - 15" above the tank.

[RICH MUISE]

I thought about that, but then one has to wonder how the tube acts as a vent if there is fuel in the low spot.....seems like it would act like a J trap in your house plumbing. I guess the answer to that is there is no spot in the oem tube lower than the position at the tank, because if there was the pressure buildup would easily blow it out, which is what is happening on mine I think?

[Ford Blue blood]

If I remember correctly the vent is all "up hill" until it makes the down turn in the quarter.....

[RICH MUISE]

Yeah, I probably need to rethink mine, but my vent tube IS at the top of the tank, so I can't go uphill.....at best I'll only be able to eliminate the downhill.

[Ford Blue blood]

If you can keep it level until the up hill in the quarter that should work.  Also, any gas in th "J" if there were one would be pulled out of the vent as gas is used from the tank.

After this brief discussion I am going to have to re-route my vent line.  Right now it comes off the top of the tank, straight back and down and will probably splash as yours does.

Once more the value of this place is self evident!

[gasman826]

The key to the stock vent not "sloshing" is the huge loop up in and under the quarter panel.  That route puts the high point of the vent some 10 - 15" above the tank.

2x

[Zapato]

To me it's pretty obvious, would Ford go thru all the trouble and cost bending and installing that vent tube if there was a simpler,safer or economical way to do so in 1957. It worked well then why try to reinvent ( or revent ) a tried and time proved design.

Zap - 

[RICH MUISE]

On my 900 mile recent trip, I filled the tank all the way, and had no seepage issues at anytime in the past 3 days. I tightened the gas cap as tight as I posibly could.....duh!!!! Probably needed the excess tightening because of the old gasket that's in these nos caps. Anyways, apparently not an issue with the vent tube.