Quote:
Originally Posted by r lane
Not sure how a crank can ''delaminate''. Pretty sure it came from a solid billet. Is that pitting and if so, what would have caused it. I think the journals are put through a hardening process that effects the surface for less than a mm in depth. I recall that they did this back in the 4 cylinder days and cutting into that hardened surface was concerning as to the integrity of the repaired crank. I think that hardening process continued into the 6 cylinders. Marine Crankshafts could probably tell you. Curious. Bob
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The cranks are forged not billet. The original Porsche cranks went through a process called "Tufftriding" a German process developed in the 1950s. It's a two stage liquid salt process that treats the surface with a nitride and carbonitride case.
What we are seeing here is
probably a chemical reaction to the surface hardening.
There is zero integrity loss to the crank if properly processed. Dave@ Marine knows his shyt. The reason Porsche mechanics were hesitant to grind cranks undersized was simply the cost of undersized bearings. In today's world that cost doesn't seem to matter as much.