I got a heckuva deal on an old AMC once because of a similar problem. Car would flood out and stall, gas would be leaking everywhere out of the carb. Owner had rebuilt the carb twice and problem was not solved. I didn't think he knew what he was doing, so I made him a lowball offer on the old clunker and he accepted just to get it off his hands. I rebuilt the carb (meaning it was left off the engine for several days while I waited to get it done). Put it back together and she ran like a champ! I was so tickled...for the first few days. Then, suddenly she began flooding, stalling, and leaking gas out of the carb. I then replaced jets. Same thing...ran great for a few days. Finally discovered that the float was actually a sink. It was not a hollow float like you refer to, but rather some type of solid, plastic material kinda like styrofoam. Seems like it had got old and lost its most important property...being able to resist gasoline. Take it out of the carb (while rebuilding several times)and it would dry out and work fine for a few days. Then, eventually, it would get soaked and become an anchor.
