My crankshaft sprocket disengaged from the shaft recently (fortunately while I was idling). After getting the engine out, I discovered that someone in the past must not have torqued the crankshaft bolt down properly, and it put too much stress on the woodruff key and eventually disintegrated it. I have had the car for four years and 40000 miles and it has run very well. The good news is that there was no significant damage to the head (no valves were bent, eventhough a couple of the cam towers broke). I have posted more about this in another thread. The car in question is a 1982 300SD, 165K.

As I was studying the situation more closely this afternoon, I noticed something tonight that concerns me. It is the keyhole in the crankshaft were the woodruff key goes. Is it supposed to be this shape, or did it get worn to this shape by the key stressing it out because of the main bolt not being torqued sufficiently? I have looked all over for pictures of this part of a 617 crankshaft and can't seem to find anything with enough detail to tell me for sure how this key hole should be. It seems to me that it should not be this shape, but then it seems that the key should be of a slightly softer metal to not allow it to wear the shaft.

If it indeed is not supposed to be this shape, do you think I could have a machine shop grind out a keyhole of the proper specifications on the other side of the shaft? Would I be able to have this done without having to pull the shaft out of the block? It seems that this would not affect the balancing, and that this should be possible.

I am hoping that for some reason I do not understand now, that this is the shape of the keyhole. Then I can proceed without having to worry about this. Please let me know what you think. I look forward to your responses.

Thank you.

Paul

Attached Thumbnails