318 Build Combo Critique

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Anyone know how much a forged 273 crank weights and how much a cast 318 crank weights?[/QUOTE]

Bob weight is what balances. (the weight of the pistons, rings, pins, retainers, rods,rod bolts, and bearings for one cylinder) That weight is totaled and added to the crank throws on the balancer. The machinist then knows how much weight to add or drill out of the crank counterweights.You mentioned running a 4 speed. Whichever crank you use it needs to be drilled for a pilot bushing.