dgmattingley

Just to clarify this point: Would a 993 cam that already has the keyway need the extra machining that Colin describes?

I checked the 993 parts diagram and found 2 sprockets and 3 cams listed. I assume the 3 cams are the early standard cam with the keyway (to go with the 911/964 sprocket), the turbo cam, and the later standard cam without the keyway (to go with the 993 sprocket). I would assume that cams that already have the keyway wouldn't need any additional machining to be used with 911/964 sprockets; is that right?

NineMeister

Simple:
If the cams look like the picture in post #9 you need to sleeve the ends to run a 964 two-piece sprocket (but ok to run the 993 one-piece, obviously).