Forged 340 Crank in a 5.9 Magnum

volaredon said

.... the "Bill from the balance shop" wouldn't be necessary because they would have the same internal balance as the stock 318 magnum crank had. And before you say '72-3 external balanced version 340 crank, those weren't forged no more. Those were cast.
Honestly I was looking something up once I. A crank kit book at a car quest some years ago and I kid you not the crank from a 318 went from at least 1967 (maybe earlier, ) to well Into the 90s. Same crank casting number. So no rebalance would be needed. Actually there were some 318s built in the 70s with forged cranks/ although not many. These were HD truck and industrial ones.

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while i am well aware of the differences and break downs of 340 cast and forged cranks (i've owned a few) and 318/273 forged and cast (again, owned a bunch), the fact remains that if you change the pistons and rods, you're likely going to need to rebalance-- and that would be 100% true if you were using magnum components with the earlier LA crank because those pieces are lighter.

i don't doubt that the 318 crank carries the same number for years and years, but just because it has the same PN doens't mean it's the same piece.

could you just throw caution to the wind and grab any ol' 318 crank and snap on some rods and pistons-- magnum or not? sure, you could. i don't know why you would unless you're trying some bobo *** uncle tony nonsense. which is fully your prerogative, you made that money spend it as foolishly as you see fit.