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The gasoline tank is devided in three cambers. The cambers are made by two tack welded division walls of steel. In the bottom of these division walls app 3" openings are located and covered with wire gauze to avoid dirt to be transported between the chambers by aligning the gas level.
In the top there are also openings to align the gas level.
I`m wondering about the functionality of the neck with the cap on the right side on top of the gas tank?
I put pressurized air on the tank and learned that the air didn`t come out of this neck. I suppose that the neck&cap is not allowed to breath air from inside of the gas tank to the outside, otherwise the gasoline is coming out here when the tank is filled up, as the top of the filling throat is 4" above the top of the gas tank. Is the neck&cap allowing the outside air to come into the gas tank when the air pressure on inside is lower? How will the air in the top of the gas tank be evacuated when the gas level is passing the height of the flange of the filling throat? By filling up my gas tank it take endless time to get the gas level above the connecting flange to the filling throat. As shown in the attachment, I have proposed to install a copper pipe from the top of the filling throat to the top level of the first chamber to secure to evacute the air in the top.

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There is a vent in the pickup assembly.

I admit the side fill neck looks like Murphy's law, but they don't seem to present problems

I'm not sure I understand the question, I have a 34 Packard with the compartmented tank; I just fill it, drive it, and fill it again pretty much like any other car. I do have to slow down the gas delivery rate a bit as the tank approaches full.

A photo of your tank would be helpful. If it is an original tank, then there should be a vent associated with the the pick-up/sender. It is very small, so filling these tanks takes patience (as Dave said).

If you are going to add an extra air relief, I suggest doing it at the top of the tank, and not modifying the tank itself.

Tom

I will look for a picture of my tank. The tank is original and the tank has as well the original pick-up /sender unit.
If it is a vent in the pick-up/sender unit, could gas come out through the vent when the gas is filled up to the top of the filling neck, because the top of the filling neck is 4" higher than top of the tank? Or is the vent so small that only air can go through?
I`m sure that I have sealing compound on the gasket for the pick-up / sender, and then I`m also sure that this vent is closed!
For sure it has to be a vent in the tank, because the filling neck is not mounted on the top of the tank, as it is for my 1929. The air pressure inside and outside has to be aligned on the 1934.
But what is the function of the small 1" high neck/cap on on top and at the left side of the pick-up / sender?
I thought this is a oneway vent. That mean: it is closed when filling up the tank, as the air pressure inside is higher than outside. And the vent is letting air into the tank when the engine is running, because the pressure on the inside of the tank is lower. Maybe I`m wrong.