Would allowing the car to sit for a month cause the float to sink if not why does it happen? I just had the float replaced earlier this year for the same thing. This is a factory 2 bbl on a 400. Is this a common problem with 2 bbl carbs?

I assume holley 2bbl?

Might be the ethanol in the gas. You may want to go to Holley's site and see if they have a ethanol resistant float.

That or it's off brand poor quality stuff.

If it's a plastic/phenolic float, replace it with a brass float, I've had this issue with the plastic/phenolic floats

Brass floats do it too, I've seen a bunch of brand new floats (regardless of the carb style) fail in this way. I have not seen a problem with older original brass floats that are cleaned up and re-used. So, it's either a new type of solder that todays fuel attacks, or just poor quality control.

Thanks guys it turned out to not be a sunk float but dirt in the needle and seat.However I think its time to upgrade my rose to 4 bbl.