Spare Crank - 3.0SC - What to do with it?
 

This crankshaft I have from a 3.0SC, measures perfect..

HOWEVER!

Some of the main journals appear to have suffered some type of delamination. Who knows how long it ran before it got to me, but yea, it was a mess.

So the question is, does this crankshaft have any future apart from a large doorstop?

Can it be reground and use 0.25mm larger main bearings to suit a stock 3.0 case?

Or can it be ground even further and used in an older 2.2 or 2.4 case? I'm not sure if that's a dumb question since I don't play with magnesium cases and am not familiar with journal sizes or cylinder spacing.

Someone approached me about creating something for a magnesium engine, and I figured, why not ask the experts who know what will fit and what won't? Maybe this crank might come in handy?

http://forums.pelicanparts.com/uploa...1750228733.jpg
http://forums.pelicanparts.com/uploa...1750228733.jpg

Grind it .010/.010, pull the plugs and have it plasma nitrided.Threaded crank plugs are certainly an upgrade Good as new.
The challenges to putting it in an early case are two fold.
What do you gain and the 9 bolt output flange.
The only benefit to the 3.0 crank over the 2.4/2.7 crank are the wider flyweights that add to torsional rigidity. The nine bolt flange while an obvious upgrade add almost no benefit until you reach 500+hp.
Some early 3.0 turbo case were modified to accept the 74.4 crank the the benefits were obvious.

I just had a 3.0L crank with the same issues repaired at marine crank. Magnifluxed and inspected, It was ground .010" under on mains and rods, Threaded plugs and plasma nitrided. Cost was $1000.

John

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

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.

ok, well I have it listed in the classifieds.

If anyone wants a cheap crank, reach out to me. Happy to ship it. I have no use for it currently.

crankshaft
 

Henry, splain. A crankshaft is machined from a forged billet of steel. Is that not how you do it. What is the diff between ''forged'' and ''billet''. Maybe we had shi**y machinest, but every broken crank shaft I have seen, 4 and 6 cylinder, had been turned. Cracked from fillet diagonally across the web. The machine procedure I was to understand, which was the cleanness of the cut and the radius, was critical at the fillet. Bob

Here's the forging process.

https://www.youtube.com/watch?v=qGwA-nV82dY

A billet crank starts life as a big bar of steel that is machined down. No heating and beating, just machining.

Well Bob, I don't know what to tell you.
Maybe the cranks you're having ground are being ground poorly. Perhaps they skip the nitriding process. Perhaps the cranks you're seeing fail, are race cranks.
One error many amateur racers make is to use parts too long. Engine parts have a life. The excesses of racing greatly shorten that life.
Most of the 911 cranks I've seen fail/crack over the last 40 years were 2.4/2.7 cranks that people tried to spin to 8K.
The flyweights are so thin that they flex causing a terminal harmonic.
Grinding a fillet radius is of course critical so when we make a "special" crank (like, 2.0, 3.2 or 964 to GT3 rod journal) we always shoot for the largest radius possible. T
his often requires us to chamfer the bearings to create the optimal clearance.
To correct the flex (improve torsional rigidity) in 2.8 and 3.0 RSR cranks they increased the radii to almost double the stock 2.7 crank, among other modifications.
The RSR rod bearings came with a noticeable chamfer.

crankshaft
 

So a billet crank would be considered of cast material. I think I remember that the early 911 cranks were not forged. An amazing video. Saw a similar set on forging the Fuchs wheel. My first thought while watching the heating and pounding, other than an environment where one could incur a life altering injury, was the constant maintenance that must be required for those types of equipment. I had heard, true or not I don't know, that the later G bodied cars, 88 and 89 I suppose, had alignment issues. Due I was told to worn out chassis jigs at the factory and Porsche was reluctant to retool due to that car coming to the end of its run. I appreciate the feedback. Bob

A billet crank would be a crank whittled (machined) from a solid ingot of usually 4130 or 4340 chromoly steel.
All early Porsche 911 cranks were forged. There was/is an unsubstantiated rumor that non-counter weighted 2.0/2.2 cranks weren't forged but I believe they were.