I'm just curious as to how a poly-lock could back off, if the inner lock screw was tight enuff to begin with. I found that AFTER I tightened the inner screw all I could with an allen wrench, I still needed to turn the outer nut a little farther, so that the lock screw would dig into the top of the stud. Since beginning to do that, I've never had another poly-lock to back off.
BUT, if you only tighten the inner lock screw with an allen wrench, & do NOT tighten the outer nut a little more, there is a very good chance that some of the nuts will back off.
All my heads had factory screw-in studs. I never tried to tap holes for conversion studs.
That's my experience. If it doesn't apply to your situation, just ignore it.
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