[69 Mach I]

I have a similar problem. I have a holley classic, 650 four bbl with vacuum secondaries (80783C). The secondaries never really opened up under WOT so the dyno tuner just bolted them open. This is not an ideal solution as it hurts your bottom end. My solution is to ditch the vacuum secondary carb and put in a 700 cfm double pumper, also a holley classic (4778C). Maybe I have a vacuum issue somewhere. Whatever the cause, the carb ain't pulling its weight and it is gone.