cast cranks are lighter by the manufacturing process. they are less dense than a forged (compressed) crank so your going to have to add weight to the throws to compensate for 1-heavier bobweight of rods and pistons or 2. lighter balance throws to begin with. I think your fighting 2, lighter throws. Tungsten is going to have to be added to the throws to make the bobweight compensation heavier. They had to use external balancing on cast crank 360 and 340 motors because the cranks were lighter by about 5 lbs with all other parts being the same as the forged crank motors so they had to add weight where they could externally, the balancer and the convertor or flywheel. I dont see an issue making it an external, you just have to supply and weighted 360 B&M flex plate and a cast 340/360 balancer, then weight can be taken from these parts. Anything can be internally balanced but at a cost of mallory metal/tungsten.
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If your going to start the balancing act, supply a weighted (cast 340 or 360) balancer to begin with. cheaper that tungsten.
