Factory cranks were balanced to a set 'Bob-weight'.

Then the rods were end to end balanced to an approx weight as long as they were fairly equal.

Some engines were close, others a country mile out!

Out of balance can manifest at different RPM's like a road wheel.
Sometimes you feel it and then you go a bit faster and it goes... drive

Somewhere around 3000 and 6000 rpm's.

You balance the crank at 1500 and the 3000 for better effect.

I've done hundreds of Mopar cranks and only ever found ONE that was right, a 340...
Big-blocks are 'suck and see' factory guesstimate... fan

Last edited by Gtxxjon; 10/26/21 12:08 PM.
Carpe diem, quam minimum credula postero, thanx Horace!

There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...