if you want to be sure the JB stays put, use a center punch and make a couple dimples on the hole edge, forcing the hole to deform inward a tad.
when the JB sets up, the inward deformation will make sure the plug can't come out.
also, there are a couple of different formulas of JB available now, and i think i saw a high temperature package at my local ACE hardware a couple weeks ago when looking for something else.