Freeze plug blow-out, 2nd time on 2nd rebuild in 6 months

[Goose]

If you guys will remember, my first rebuild last spring ended my relationship with my mechanic after a number of failures, one being a blown out original oem freeze plug that he neglected to change out when boiling the block. That resulted in a warped head and another trip back to him for repairs.

So after a couple hundred very happy miles on rebuild number two from mechanic number two, I had another freeze plug blow out this morning. I didn't see the temps soar as bad as the first time and don't think I warped the heads again but what the heck is going on?

I had told the 2nd mechanic all about the first guys failures and so he even JB Welded fresh plugs in on the 2nd rebuild just for added insurance. I have to believe theres a common denominator here but I'm clueless as to what it could be. The original plugs lasted almost 50yrs and blew out with the first rebuild. I had put a new 7lbs radiator cap on a year before the 1st rebuild without any issues. Any guesses?

[Bruce W]

Goose, sorry to hear you're still having trouble. Is this plug in the same position as the other one that failed? Which position(s) are we talking about? Did the original one truly "blow out", as in remove itself from the block, or fail & leak because of rust, etc? And the latest one - I'm assuming it came out. I don't know about the JB Weld idea, seems to me that the proper plug properly installed should not need any more than the normal Permatex #1 or #2 (that's what's normal in my place, anyway). I don't know how well the JB Weld would react to the heat and expansion/contraction of the block and plug. BW