[buzzinhalfdozen]

Freddie Sounds like it's not so much the engine as the combo itself. You need to give more info, gearing tire size weight RPM ect. I built a "very" mild 347 for my nephew this summer small hydraulic rollercam flat top pistons victor manifoldout of the box holley runs on pump gas with stock fuel pump and fuel system, he street drives it. At the track on street tires with 2500 converter spinning most of first goes 11.70s no slapper bars or anything, so I'd say it's your combo. Joe P.S. this is assuming there is basically nothing wrong with your engine ie. totally wrong cam,carb,or tune