Yesterday I set out to do a simple swap - remove the Prestolite system and install an MSD distributor and Street Fire ignition box. Simple, right?
The first step is swapping gears. Both the old gear and MSD gear came off easily, and the old gear slipped right onto the MSD shaft. But the roll pin holes didn't match! I had a 2mm difference in the hole placement. I called MSD tech support thinking I just needed a few washers to take up the space. Not so! The tech said that swapping gears is definitely the right move with an AMC V-8, but additional washers would just get eaten up and lead to gear failure. The solution - rotate the shaft 90 degrees and drill a new hole. Sure - drill a STRAIGHT hole the EXACT diameter into a HARDENED shaft to establish the proper END PLAY. What could be easier?
I set the new dizzy in the vise and started with a small bit, and discovered the shaft isn't that hard and was easy to drill. My wife eyeballed the procedure to ensure I kept the drill perpendicular. I drilled the hole three times slowly increasing the size and the fourth time was the final bit. I installed the gear and pin and I had ZERO end play. Not good. I only had one option, and that was to try to waller out the hole slightly and it worked! the gear installed nice and tight and I have 13 thousandths of end play.
Just to double check the gear meshing, I coated the gear with Prussian Blue and installed the dizzy, then cranked the motor 5-6 times. I removed the dizzy and found a nice pattern on the gear teeth. The rest of the conversion went smooth, and now my old familiar Prestolite idle is gone forever.