Originally Posted by lumpster
Ive never had a spark plug back out.
I recently learned its a larger problem on aluminum head engines. A friend of mine blew a plug out of a Ford 5.4 Tritan engine ~2 weeks ago...plug backed out till it finally ripped all the threads out of the aluminum head on a compression stroke, while driving down a country road
. His mechanic found three others about to go. apparently the cause is heat cycling + improper plug torque + no loctite...and Ford makes a heli-coil specifically for this issue. so...torque your plugs to spec!