FUEL LEAK BY THROTTLE SHAFT(S)
A common complaint today is fuel dripping out of the throttle body by the throttle shaft AFTER the engine is switched off. While a number of issues may cause this problem, by far the most common issue is the volatility of modern fuel. Mechanical fuel pumps have a check valve which prevents fuel from moving back to the fuel tank. The problem is as follows:
(1) After the engine is switched off, heat from the engine heats the fuel in the fuel line.
(2) The expanding fuel (increased volatility) creates pressure in the fuel line from the pump to the carburetor.
(3) The check valve prevents the fuel backing up through the fuel pump.
(4) The pressure increases to a point the float/fuel valve combination in the carburetor cannot withstand the pressure.
(5) An amount of fuel (usually from a teaspoon to a couple of tablespoons) flows into the fuel bowl of the carburetor.
(6) This raises the fuel level in the bowl above the main discharge nozzle(s).
(7) Fuel flows through the main discharge nozzle(s) and drips onto the throttle plate(s) which is/are closed, and exits out beside the throttle shaft(s) dripping onto the intake.
(1) IF POSSIBLE, AVOID ETHANOL LACED FUEL! Sometimes you can buy real gasoline at a marina
(2) Buy the lowest octane name-brand fuel that does not ping or detonate in your engine (the higher grades often have more ethanol)
(3) Install a “vapor return line” (take a look at return lines used on many factory air-conditioned cars)
(4) Learn to live with the issue.
Above material copied from : THE CARBURETOR SHOP trouble shooting section
#4 -learning to live with the problem is not the best solution.
Nothing worse than getting behind the wheel and smelling raw fuel leaking,
Right combination of conditions could be disastrous or even tragic.
One thing I have had to resort to is insulating the fuel line where it passes close to the exhaust system and all fuel lines inside the engine bay.
It makes a huge difference given the propensity of today's pump grade gasoline's to percolate at higher temps.Fuel injected cars are not as sensitive to this.
If the fuel system gets heat soaked (stop & go traffic) the fuel will percolate and cause cause low speed drive-ability issues until the temps drop sufficiently and allow the fuel to cool. Excessive heat soaking of the Carburetor & fuel system when the car is parked after running will also cause problems as described by the CARB SHOP info.
Find a way to vent the hot air out from under the hood.
If the ram air scoops on the hood are non functional open them up to get some cooler air entering the engine bay.
Sometimes a 1/2" 0R 3/4" spacer between the the hood and the hood hinge pads will help to get rid of excess under hood heat. Not pretty but have had to resort to it and the results were positive.
A carburetor heat shield and thick carb base insulator may be in order .
The heat shields are EZ to make at home out of sheet aluminum ( Moroso & other companies used to sell them ready made ,just trim to fit).
Mr. Gasket still sells the base insulator kit for the Q-jet
Hopefully the condition your carb is exhibiting is a simple fix or a combination of simple fixes.