Crankshaft runout issues

[Maximum E30]

So I've got three crankshafts,

#1: 0.003" TIR, decent bearing journals
#2: 0.0005" TIR, and fairly worn journals, not horrible but you can feel the grooves with your fingernail.
#3: 0.0025" TIR, and perfect mirror bearing journals.

Now the question is, which one to use...

The crankshafts are all forged, this is for a turbo motor that will see some pretty high Hp/torque. I've looked around and it seems like straightening a crankshaft isn't unheard of but I'm not sure if it would have any effect on the longevity. I have a hydrolic press that I could put a load on the one with 0.0025" TIR and get the bend out if it, but I'm worried it will come back once its in and running in the engine. Our bearings only have ~0.002" clearance, so it would be rubbing if nothing is done. On the other hand, I can push down on the crankshaft and get it to spring 0.001" fairly easily, so maybe there wouldn't be much of an increased load on the bearings with it having 0.0025" TIR. I'm having a hard time finding a good crankshaft and don't want to spend anymore money gambling on if it's straight or not. Does anyone have any experience or do most people not even bother checking? Let me know what you think, thanks.

[TobyB]

I have also wondered this. The current 'hot' Pro3 engine builder has them straightened-
"they're all bent"
but like you, I can push on a crank and get a thou or sometimes 2.
Wanna watch something fun? Heat one side of it with a heat gun...

So I dunno. I'd say spam the Pro3 list, but anyone who says anything won't know anything!
(heh)
I was going to practice on a spare crank with a brass mallet. Really.

t

[e30davie]

I have no real experience to offer...but what is the bmw spec on crank runout?

And have you checked the line bore straightness of the main bearing journals in the crank? Presumably you could have a dead straight crank and your block is slightly bent making your main bearing journals not straight then you could have an issue anyway?

Unless you intend on line boring your main journals? or maybe "modern" blocks don't need line boring....

[packratbimmer]

Most engine builders I have known hang cranks for storage due to this issue. They will settle over time. That's why I store them in their blocks. Makes me wonder if one should hang a crank and let it reach temperature equilibrium before checking???

[zaq123]

all 3 of those cranks are still within spec, 0.0059". I would just go with #3 one for obvious reasons.