I have a MP forged crank part number 5007254. 4" crank for a 360. It's supposed to be for internal balance. Never used and still in the box.
The machine shop called today and said it's out of balance 119 grams at the balancer and 146 grams out at the flywheel. They don't act like they can add or take out enough metal to internal balance it, so they are suggesting external balancing.
Did someone drop this thing and not tell me?
Think Mopar Performance made a crank this bad out of balance?
Is it worth fixing and worth the machining costs?
Should I make a lamp out of it and buy a new Scat or Eagle crank?
Thanks!

That isn't jack squat, fire those goons. 300gms remove is about where you start getting excited IMO. S/F....Ken M

If it's light it need Mallory metal. If it's heavy I'd turn the counterweights down first and then drill small holes.

You'd have to have a Flintstone style bobweight to have end weights that light.

If they can't turn the counter weights and drill some holes maybe need to start over.


Just reread OP and they want it external. How heavy is the bob weight? To ADD that much weight the bobweight must be 2500 grams. Or more.

Something is wrong

I have the same crank using with Scat I beam rods and KB744 pistons..it has mallory metal in front and rear counterweights...

that mopar crank is a Scat crank....

If that's an add, that's two pieces of 1" tungsten, per end(actually, probably one 1" and one smaller piece). It's probably about $400 worth of work there, but it should be doable.

I'm uncertain why it's an add (or 100+gms) if the crank was "designed" for internal balance. What parts are you using? S/F....Ken M

Scat made LOTS of cranks that were out a mile for normal bob weights--
That is the deal

The rods are Eagle h beams - 680gm

The pistons are ICON forged dish IC745.030 - piston is 517 and pin 118.

I don't want to bother buying another crank and have the potential to have the same issue. I think they were surprised that an internal balance crank was that far out of balance.
I didn't think to ask at the time if it was all adding weight, taking out or some of both. The comment "swiss cheese" was made.
I appreciate the help.

That makes sense then because from the looks of his parts his bobweight isn't abnormally high.

Pretty [censored] deal they say it will internal balance and it doesn't have enough mass to do it.