it was bothering me that the tightening of the set screw could have such an impact on the distortion of the housing.
So I went to the garage and loosened the set screw. I then felt the turning resistance of the shaft with the screw loose, and then again with the screw tight. There was a difference, albeit only a little. Well I'll be! (I did this test with my newly-installed freshly-rebuilt distributor)
So I concede, the screw should only be snug, not tight...and that's how I set it.
