2V help needed

I wish I could explain the pressure diferential in simple terms. Ever had a tire that would leak from 35 psi down to 15 psi but never go completely flat ?
Anyway.. that pressure factor is what forced fuel into the float and let some of the air out of it. The fuel wouldn't leak out again with the float just laying in a neutral atmosphere.
Parts for these older carbs are nearly impossible to find. Your best bet is find another whole carb. A 318 2 barrel will work on a 273 just fine.