FWIW:
One (1) humble opinion on a most common, Model A fuel leak problem many will not want to pay for nor even admit.
1. Appears if we have a Model A carburetor float valve leaking problem, we are definitely in the Model A owner "majority" with having such constant leaks; however,
2. Appears also if we report that we have a constant Model A carburetor float valve leaking problem, we are in the Model A "minority", because very few of us Forum members want others to think that we are not perfect, and we are not great Model A mechanics who cannot resolve what appears to be such simple, small Model A mechanical problems. But is it always simple?
3. In my humble opinion, most of our float valve problems stem from our leaking fuel tank shut off valves, and more importantly, from our fuel storage sources further up the fuel line.
4. If our fuel shut off valve never leaks, our carburetor fuel shut off valve would never leak if we shut off the the fuel line first and allow our cars to run until there is no more fuel in the carburetor.
5. The Model A fuel leaking problem source is always further upwards, such as:
A. Our fuel tanks are approaching 90 years old with failing interior original coatings; more rust particles are forming as time goes on; former fuel tank sealers are being dissolved with ethanol gas in some cases; almost 90 years of collecting dirt and other deleterious materials at bottoms of tanks are still there, all of which break down, lodge in our soft brass fuel shut off valve and causes this fuel shut off valve to leak.
B. Next, with our engine operating, with our shut off valve opened, these same very fine fuel tank impurities pass through our fuel filtration system, and lodge in our Model A carburetor float valve, and also causes this carburetor valve to leak.
C. An additional problem is our Model A limited use where most problems occur when we do not drive our Model A everyday; hence, just like our Model A valves that collect varnish and get sticky, so do our carburetor float valves.
(Just think, even our bathroom toilets get dirty with clear water, (water clean enough to drink), if we only flush them once every four (4) months.)
D. Another problem is fuel gravity flow where a more modern fuel pump does not quit pumping fuel when our engine stops; hence, with a Model A leaking fuel shut off valve, and a Model A leaking float valve there is constant Model A gravitational fuel pressure exerted from the tank to the overflowing Model A carburetor bowl at all times.
6. Is there .......... without a doubt ....... a 100% positive solution? Yes.
7. But not for most of us Forum members where most of us are a bunch of Tight Wads and far too tight to pay to have this problem properly corrected, such as:
A. Have Mr. Brent in Tennessee "properly" restore the corroded "interior" of our fuel tanks; and,
B. Buy a new fuel shut off valve and new carburetor float valve; and,
C. Last but not least, drive our Model A more often to keep fresh fuel flowing at all times.
Hope this helps any future Model A owner whose house and garage could burn down to the ground because of a parked Model A leaking lots of gas through an overflowing Model A carburetor bowl.