Yep, the insert unscrewed with the glow plug during the CDI conversion. Truth be told I spec'd the length of the insert wrong. The glow plug hole on Saitos is canted with respect to the roof of the combustion chamber, which I knew ahead of time, but somehow spec'd the insert length 2 threads too long anyway. The swaged portion of the insert only engages the cylinder threading around 60% of it's perimeter. Perhaps that explains why the swaging of the 2 bottom threads was so easy. In addition I used JBweld only on the top 2 threads of the insert, none on the insert flange, and didn't ham fist tighten the insert during installation. It was tight enough to remove the glow plug with uncured JBweld, so I figured good enough. Wrong.

This time I used JBweld on the top 3 threads as well as on the insert flange and tightened the crimeny out of it. Might hold now.