Crank Machining?

Turbong2001

Registered User
Ok, so i have head that the 3.8 can't be machined because of thickness issues, and have also heard that the bearings are special bearings, what the facts here. I'm going to pull a 3.8 apart and want to know what all the fuss is about!
 
My rod journals are turned down .010". I made 450hp to the wheels. Knock on wood.:) Been beating on it for about 7 years.
 
Stock SC crank journal and rod surfaces are nitride hardened. most people feel .010 is fine to turn the crank before having to have it re-hardened. Go further and you increase the risk of loosing the hardening and ending up with a weaker crank.

The SC block and crank has one main journal sized different than the others thus requires special bearings to fit. This was done to reduce the chance of a NA crank being used in an SC block.
 
You have to redo the fillets at the edges of the journals correctly, or you will get stress risers and, most likely, snap the crank.

If you do that correctly, some level of undercutting is safe. What level? Well, I really don't know.
 
The maximum you can turn the SC crank is .010" according to the Ford service manual.

I had my crankshaft turned .010" on the rebuild but this was due to a rod knock so the journal had been worn more than normal.


- Dan
 
The maximum you can turn the SC crank is .010" according to the Ford service manual.

I had my crankshaft turned .010" on the rebuild but this was due to a rod knock so the journal had been worn more than normal.


- Dan

I think that's partially based on the fact that the rear journal is 0.010" undersized to start with ... so that journal could end up at 0.020" undersized after machining. If one of the other journals was the damaged one, you might be able to go past 0.010" on those journals and still be okay. Just a thought.
 
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