[chopper]

Just an observation on the spacers. Carb spacers generally serve two purposes: (1) to provide a longer (read: straighter) flow path to smooth out the turbulence of the air entering the venturis and (2) blockage of heat transfer between the intake manifold and carburetor. Aluminum spacers will accomplish #1 but will have essentially no effect on #2. If it is, indeed, a heat problem, you may wish to try some phenolic spacers which will help insulate the bottoms of the carbs from the intake manifold.