[Pete]

Here is how I do the cam timing adjust thing on a Ford flathead engine.
I use an early press on timing gear core, usually steel.
I put the crank gear on ONLY far enough to match the cam gear which I only press on about 1/16 inch at the factory marks.
I degree the cam per standard procedure.
If I need to move the gear, I pry it off, move it and knock it back on at the new location, then recheck it. It only has to be on far enough to not slip. 1/16 or LESS.

As far as knowing how far to move it requires some math.
The drive hub is 2.624 dia. so is 8.23 circumference. Moving the gear one way or the other 1/16 inch from the factory mark will give you 3 degrees. (Eyeball resolution)

After I determine the final location I drill and tap for a 1/4-20 set screw on the parting line of
the gear/cam.