#3 sparkplug blew out of block. Threads stripped. Rethreaded with Flexicoil. Worked okay for awhile, then happened again. Tried Loctite as a temp fix. Won't take the heat, blew out again. Friend suggested Propoxy Plus epoxy steel (used in plumbing). Any idea if this would work? Not concerned about getting plug back out, just getting it to stay in place. The car has 271,000+ miles and runs great. Thanks! Bill Barton