Ok, about those left hand threads.... I rather did this for Captain John, but I think he's on vacation.

Anyway, here's some pics and instructions on a good fix.

The first one shows the crank all taped up to keep the bearings somewhat clean, chucked up and centered in the lathe, and being drilled down the factory center bore with a number 29 bit. I drilled this pilot hole as deep as I wanted the stud to eventually go, which is approximately 1.5". I ran the lathe very slow; so slow that I could almost count the revolutions, and had no problems. Just go slow, don't force the bit, and use a little cutting oil.

The second pic shows getting ready to part off the left hand threads. There are two advantages of using the factory counterbore to pilot drill the crank first. One is you don't need to use a center drill to start your new stud hole, and the other is that the left hand thread portion can be parted off easier after you've drilled the pilot hole.

The third pic shows re-checking the centering after the parting operation. The crank is now ready for drilling the hole to be threaded for a stud, right down the pilot hole drilled in the first step.

Pic four shows drilling the hole for the stud with a "I" drill. (This is for a 5/16" x 24 threaded stud)

Pic five shows tapping the hole 5/16" x 24. Be very careful to get the tap started straight, as the hole will most likely have just broken into the bottom of the key slot. It's no problem, just work carefully. (That's why I made the hole about 1.5" deep into the crank; to have good support beyond that key slot.)

And pic six shows the completed crank, ready for a stud and a normal prop adapter setup. Now when I start this engine up, I won't have any worries about the prop coming off, and I think this is an easier operation than making a custom prop hub to accomodate the left hand threads. Also, no matter how well you taped the crank up to keep it clean, I recommend a thorough cleaning, blowing out, and re-oiling of the bearings before you assemble the engine

Hope this helps someone,
AV8TOR