I need some help figuring out a surging vibration from 2400 to 3200 RPM. Below 2400 smooth above 3200 smooth no vibration. The motor specs are listed below. I have tried different trans, converter, drive shaft, timing, rear end, tires, carb, the converter is a hughs 3000 stall and a PA C4 trans.
any help would be great.
Thanks Dave

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Ford Racing 347 Short Block Edelbrock performer RPM Heads Air gap intake MSD 6 AL Ignition Demon 650 carb Crane Cam Hedman Headers 2.5" Flowmaster 40 series 3.55 Gears Aubrun Gear Pro series