Engine/drivetrain vibration?

DartSportDude said

- After talking with everyone involved in the engine rebuild, it appears the machine shop did NOT include the TC for the cast crank engine when they balanced the motor. Thus, it appears the balancing might have been done to the specs of an earlier (internally balanced) 340 -- not a externally balanced '73 motor

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Was it internally balanced like an early 340? The early 340s are internally balanced and have neutral balance vibration dampers and neutral balance torque converters (no weights). It sounds like they aren't sure or maybe I am reading it wrong? If it was internally balanced like an early 340 then a neutral balance 340 vibration damper would fix the problem. No weights are on the converter now so nothing would need to be done there. This is all assuming it was internally balanced like an early 340 which I am not sure they did?

Here is an internal balance vibration damper:

http://store.summitracing.com/partdetail.asp?autofilter=1&part=DCC-4452816&N=700+115&autoview=sku