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I hope this doesn't sound stupid but I am trying to digest this internal/external balance issue. If the 440 truck engine has standard rods it will be internally balanced and I can use the 69 727 convertor and all? I assume I need to use the existing balancer that is on the 440? Now, if it has the H duty rods and crank and is externally balanced what if anything do I need to do in order to use the 69 trans.? I always thought the harmonic did the work no matter what crank and rods it had? How else could it be externally balanced unless weight was added to the flex plate? I am still a little confused here? I just want to avoid vibration issues with this project.



Weight is not added to the flexplate it was added to the torque convertor by the factory. B+M sells a weighted flexplate , but it's not really weighted it has a big scallop out of it OPPOSITE of where the weight would be added on the torque convertor. By using this you can use ANY NEUTRAL balance convertor you want and not worry about the balance issue.

Part of the reason the HP engines were external balanced was because of rod AND piston weight, it's not hard or costly to internal balance a big rod motor. Ignore the rods, what balancer is on the engine ?