GAS TANKS

Q: How can one tell an Austin gas tank from a Bantam?

The short answer is that the sending unit hole for a Bantam tank has five mounting holes, while the Austin has six (and the whole thing is nearer the firewall/big end of the tank). The gas tanks of the two cars look pretty much the same and are easily confused. With my emphasis added, here is Norm Booth's explanation on how to tll the difference, or what to do if you have one and need the other. "They are both the same except for the location and bolt circle for the gasoline guage sending unit.

On the American Austin tank, the sending unit is the atmospheric bourdon tube type by King-Seeley Corp. The sending unit is fastened into the top of the tank quite close to the larger end of the tank (firewall end).

There six 10-32 NF tapped holes in a backing plate. These holes are equidistant radially on a 0.974 / 0.964 inch radius from the center of the sending unit.
The Bantam sending unit is a Stewart Warner 6 volt electric unit mounted on the top of the tank with the center of the sending unit 7-3/16 inches from the larger end of the tank. (firewall end) The unit is retained by five screws on a 1-1/16 inch radius bolt circle which are not equidistant.

The tanks can be converted from American Austin to Bantam or vice versa by blanking off the existing sending unit hole and cutting a new hole in the proper location. The sending unit can be retained with sheet metal screws and sealed with a gasoline resistant type of Permatex. Make sure the Bantam sending unit is well grounded to the gas tank, or run a separate grounding wire.

Further note

The Austin outlet valve is more towards the middle..if used in a Bantam this is right next to the sparkplug. where the factory drawing shows it is located, for aBantam. The fuel outlet opening for the American Austin gas tank is about 3 inches inboard from the right (Passenger) side of the tank. The reason for the difference has to do with the spark plug locations for the
cylinder head. The spark plug location for a American Austin is directly
over the piston, almost center. For the Bantam. the spark plugs are
located over the valve chamber, which is to the right (passenger side) of
the piston location.

In summary, the major differences between the gas tanks on Bantams and
American Austins are: (1) location and number of screws in the retaining
flange of the tank sending unit, and (2) location of the fuel outlet
opening, and (3) some Bantam gas tanks had reinforcing angle on the bottom
of the tank.

My main concern is safety and access to open and shut off the gas cock.
With a Austin gas tank in a Bantam, the gas cock is right up against #4
spark plug, and that is very inconvenient as well as a real fire hazard.
In order to use a American Austin gas tank in a Bantam, along with
relocating the tank sending unit, and it's retaining screws, one should
relocate the fuel outlet hole so that it is the same distance from the
bottom of the tank as before, and to the center of the lower right side
fastening tab. This is a move of about 1-3/4 to 2 inches.