318 with Carter 2-bbl fuel leak through throttle shaft after hot engine shut-down

It is called "modern fuel." Oxygenated/ alcoholized fuel.

Soon after I got my 67, and swapped in a different engine, I endeavored to duplicate the fuel vapor return system used on the hemi and 440 cars. You can buy fuel filters with a built in orifice / 1/4 return fitting. You will have to safely add a return to the tank and figure a way to get the return into the tank.

I also used a thick insulator base gasket.

Other issues are too much fuel pressure and poor/ leaking needle and seat, as well as mis-adjusted float level.