fuel problem

i have a 1970 plymouth duster with a 340 ci the engine has been majored bored 030 over forged pistons oe cam part#4120233 292 duration 508 lift the original carter avs was overhauled and installed after timing was set i kept getting fuel dripping from vacuum boosters so i removed and installed a six pack set up that i had same problem i sent the six pack to promax carbs they went thru and set uo on their test cell engine installed on my car same problem checked float level needle and seat on both set ups is it possible that cam is causing problem thanks