NO do not use locktite. i am retracting this now after what i saw today on a test i did. and i showed it too my boss. to start off i take responsiblitiy of this but we were told to do this on new lightings ( by ford back in 2002-3) and was recomended to use this method for all mod motors. it turns out that while the locktite does stop the plug from loosening and backing out. it can cause some thread damage. i must of got lucky on my car. i took a 5.4 with a spun bearing we had in the shop. this motor had plugs put in by us at 100k miles with locktite and the motor was pulled at about 139,000 i removed the plugs from it as a test 7 of the plug holes the threads were fine. one of them showed some thread damaged. and upon closer inspection i think this could have been caused by the locktite. i showed this my boss who was working today. and we are going too look into it. i think when this was told too us by ford they knew that the locktite will stop the plug from backing out. but they probally never considered removal. they were proballly only concerned with stoping the plugs from backing out and with a 100k plug they figure it will be well out of warrenty. i gave ford a little more credit than they deserve and took this as meaning that it's safe. i must have gotten lucky on the ones i did remove well i have used locktite now on a few mustang and lightings i work on personally and if a problem comes up i am going too get them free heads. i checked mine again and showed no thread damage. so i put in another set of plugs after i cleaned the threads. so now the only thing i can think of is the tried and true tourqe it down too spec and recheck them once in awile. well i am not perfect and i doubt many of us are.