[H. L. Chauvin]

Hi Wayne,

When filling a Model A tank out of a gas can, through an open funnel, this usually never happens.

If filling a Model A gas tank out of a gas pump with the large round rubber anti-back-splash device, un-vented air can get trapped in the tank until one removes the nozzle ...... then after the seal is broken after the nozzle is removed, very similar to a human physical reaction with excess interior air, the gas tank burps, (in this case, naturally, from the "top" end), and forces liquid gas out of the tank

Not to be facetious, but one (1) other guess if this happens "without" trapped air:

Might have something to do with one's daily zodiac signs.

If it were me, next time it happens, I would try depositing $1,000.00 in my savings account to see if it overflows.

One will never know until one tries it ..... stuff happens !