Boy, I had promised myself I wouldn't jump into this thread, bt here goes...

I don't think anyone is saying the crankshafts themselves are balanced the same. I was saying, and I think others were saying this too, that the bobweight to balance either crank would be the same, assuming the cast crank carried with it all its factory imbalance gear, such as flyweheel and harmonic damper. The rods are the same in all four cases and Chrysler was very good about keeping things weighing the same to reuse or keep using crankshafts.

My best example is the extra heavy wristpins that they used in 273s in order to keep using the Poly 318 crankshaft and rods in the 273. The extra heavy wristpins made the 273 and 318 piston/pin weights equal.

R.