mopar crank

[Myron Piatek]

Originally Posted by George Mirza

It will fit, but it may not balance properly. 340 cranks have a hole through the rod journal to offset the piston/rod weight. Also most 340 cranks are steel and most 318 cranks are cast and externally balanced. Find a steel 340 crank and do it right, you'll be better off in the long run.

George,

All 318 cranks, cast and steel, are internally balanced, as are 340 steel cranks. (All have neutral balancers/dampers & converters.) Only the 340 cast crank is externally balanced (and 360's).
But balance will need to be checked anytime you start swapping parts around. 340 pistons are obviously heavier than 318 parts.
I use to hear that the steel 318 truck crank was a good, strong piece because it didn't have the journal holes.