One for the techies on here. I've got a YB crank out of a standard 2wd Sierra, the crank spun No.3 bearing and after being checked by my local cylinder engineering firm i've been told that it needs 5 thou taking off of the bearing journal but it's bent by 35thou. It can be straightened.

My question is, i've had dealings with straightening cranks on run of the mill standard vehicles with no upsets, but is it ok on a YB that I want to Blueprint and then Stage3? What possibilities are there for failure? I have my worries but wanted to check on here.

Regards

 

Realistically it's scrap now.
They can be straightened, but no warranty will be given, and even on std power would be likely to fail again.
My machinists have a specific machine for straightening cranks, and they won't even take it on, it is used mainly for older stuff and agricultural stuff.
I would be very surprised if it was not also cracked, if it was a non steel crank it wouldn't be so bad but on a cossie crank forget it.
tabetha

 

Id try and find another crank personally.

They may be able to effectively straighten it by machining the journals undersized offset so they are all in line again, without phsyically straightening the crank though.

 

I would ask myself is it really worth taking the risk, if you go ahead and it goes bang, you are gonna be pretty f**ked off! Source another one and go from there.

 

Not with a 35 thou bend in it they wont.

 

Pretty much what I was thinking to be honest but thought it worth asking first.

Cheers people.

 

They can straighten it by bending back into shape, it uses a series of supports on the edges of the journals, and physically bends it the other way.
tabetha

 

I used straighten bent shafts at work between centres using a big hide mallet and a dti really bad ones would go on the press first resting on v blocks to get them somewhere near

 

I got mine on the anvil and straightened it with a hammer.