There is a fuel filter with a 1-way check valve in it that's supposed to prevent fuel drain-back, but you've probably got the classic leaky float chamber that was common on a lot of QuadraJet carbs. It requires a teardown and rebuild, but a coat of epoxy similar to J-B Weld applied to the bottom of the float bowl where some drilled passages are plugged will eliminate the leak. Find a tech who knows what he's doing for the rebuild, as the average Quad has 23 consecutive adjustments to make on reassembly, and most of them are very critical to proper operation.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!