The use of an impact had nothing to do with this problem. If the bolthole was too short, or the bolt too long, the impact did not cause the problem. Someone else wrote something earlier claiming that they installed the dampener and bolt, and the washer was "free." This indicates to me that possibly some cranks are not tapped deep enough.
I know on the BB engines, at some point there was a change in the cam drive----is it possible that some folks are getting thinner sprockets than original?