Engine/drivetrain vibration?

DartSportDude said

"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?"

This sounds like a logical solution, however, wouldn't you still need to perform some kind if balancing on the drivetrain -- even if you now have a neutrally balanced engine, torque converter and harmonic balancer? This approach might improve the vibration, but I still don't see how the drivetrain would be fully in balance. Making I'm making this too difficult.

Thanks

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On an early 340 which is internally balanced the vibration damper is neutral and so is the torque converter. Therefore they don't need to be balanced. I did take my new vibration damper to the shop and have them check it to make sure it was truly neutral balance though. But in general, no, an internally balanced engine does not need its torque converter and vibration damper balanced but its not a bad idea to have them checked to make sure they are truly neutral.

Also, in your post above, you talked about going with a neutral balance damper and B&M flex plate. The flex plate is only needed if its externally balanced. Do not change the flex plate until you determine how the engine was balanced.

Did you go with lighter aftermarket pistons? If so what did they weigh? You can find out if you get the part number and look them up. If they were much lighter then the originals they might have been able to balance it internally with out adding mallory to the crank. If the pistons weighed close to the originals mallory would have to had been added to the crank to internally balance the engine. If they had to add mallory to the crank that is not cheap to do and you would see that in the bill. I would think they would remember that also because its a bit of work. So finding out what pistons were used and how much they weighed would really help in figuring out what they did.

Did they take the original damper into account or just assume it was neutral balance and set it aside when they balanced it? I don't think it would balance correctly with an external balance damper and no weights on the rear to simulate the external balance torque converter (or flex plate).