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Discussion Starter #1
Hi

I'm searching some information about regrinding the crankshaft from a v6 engine. Does any one have experience how deep this crank can be regrinded? It seems I have to go 0,75 mm. And where to find bearings for this size.
Anyone knows who can make special order bearings?
The reason for doing this and not swapping the defect with a new one is that this crankshaft is internally balanced and I think if regrinding can be done it's easier than making the internal balancing.

Hope some one can share some information with me.

Thanks

Mende
 

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Hi Mende, seems you have done a lot of work on the crankshaft! I think your best alternative is to regrind journals as necessary, then hard-chrome-plate back up to original size and you will be able to use std bearings. If the job is done properly by a reputable shop, you will end up with an excellent crankshaft. I did the same job on a few journals on a 2liter crank ~20 years ago and it still runs well.
Cutting the journals undersize is also possible but you would be advised to have the crank nitrided again. In this case you can look to match bearings from some other make/model which should not be too difficult if you have access to some Federal Mogul parts books. In this case, I suspect you would also have to use new rods with smaller big-end diameter. Good luck!
Jim K.
 

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Discussion Starter #4
OK, so first ground has been done, the crankshaft look like new. Unfortunately one of the rod big end bearing had to be ground up to 0,75mm. These bearings does not EXIST :oops:.

So now we are back to the hard chrome methode. I need to add 1 mm and then grinnd it to the same dimension as the other, so all are identical.
 

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Hi Mende,
Unfortunately, there is no single standard for nitriding depth. Some people accept .005" and others want .030". I don't know how deep Alfa nitriding goes so we are in the dark. The only way to find out would be to section a journal and do several hardness measurements... Very interesting but far from everyday jobs! However, people were still building durable engines 40-50 years ago without nitrided cranks! I believe that with proper line-boring/clearances/balancing/oil quality and pressure, even a standard crank would work great and last a long time!
Jim K.
 
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