Anyone Else Have This Problem?

[metaldad]

Gas tank getting pressurized, forcing gas up and out the vent line that exits the trunk behind the rear seat.
68 Coronet 500 convertible, (new to me). New gas tank, lines, vent lines by previous owner. Mechanical fuel pump. I checked my shop manual, seems the routing of the vent lines are correct. Non vented cap. Releasing the cap, lets pressure escape, vent drip stops immediately.
Google search, remedy on multiple sites (various brands have this problem), seems to be drilling a small hole thru the gas cap.
Someone here has to have a buggy similar to mine.
What do the pros here state
Thanks for reading, and any replies.

[ws27]

Can you find a vented gas cap?

[metaldad]

no. a large after market manf., slant, does not, after inquiry
whats on your car, ws?

[ws27]

I have a 67, so the fill pipe configuration is different. But it is vented.

[metaldad]

so, no one else, eh?

[67440Dodge]

dang..I thought I replied.

I had this issue on my 67, it was due to the rubber vent hose got pinched from the tank to the metal vent line. Once I cleared it, the tank was ok.

Don't run a vented cap on your car. The location of the cap is not conducive to using one.

One thing you can do is disconnect the vent tube line to the tank, and connect a rubber hose to the tank and run it up high so fuel won't spill out. Drive it around a bit and see if the tank pressurizes. If it does, the vent line on the sending unit may be plugged or pinched. If it doesn't, it sounds like there may be an issue in the vent line itself.

[metaldad]

well, i'm usually busy with work, then the dilemmas that arise from the house.
i finally got around to really reading my shop book, and comparing to what i have.
shop book calls for (1) vent line leading from the passenger side up, through the trunk, and around it, and back thru.
seems that is not the 'leaker'
there is a second short, as in real short, vent line, at near the level of the rear axle, that dumps fuel when the tank gets pressurized.
i have NOT checked (yet) if the lines are clear - but - i think(?) i should plug this 'short' vent line, giving me 1 that actually goes uphill before terminating.
input?