Mustang92 said:
If it was directed at you I wouldn't beat around the bush I would name you. Please do not put words in my mouth. The reference is to the dozens of cases of heads with the plugs blowing out and you are not the first or last.
This is direct at the question above the 4 threads in the heads are not strong, over tightening them even from the factory is enough to weaken them to the point that cylinder pressure will blow them out over time. The fact that most people found them with the plug still fully threaded into what was the threads from the cylinder head makes it pretty obvious that it had nothing to do with plugs backing out of the cylinder unless they managed to back out then back in after they blew out of the head.
Just because a plug blows out of the head does not mean it was due to it backing out. In fact there is little to nothing to support this other than one person saying that Ford recommends loctiting it but yet he can't provide anything to back this up from Ford.
Mike for the record the posts I have are 95% helping people from this board up till 2 years ago when BS info like this just got too annoying to deal with. What your suggesting here is not only wrong but could cause some serious problems for people.
Bill
Bill, i got this info right from ford. if you don't think it's a good idea then don't do it. but i personally will trust what ford tells us more than this forum. I am not a engineer i just turn wrenches. maybe it is a bad idea. all i know is i originally heard it from a offical ford boradcast message. we talked about it in the shop for a while and was pissed that we had too pull plugs on brand new lightings and put locktite on them .
WTF would ford have us do that if it was bad, horrible or wrong.
OK this will be the 4th post now that i will say this.
IF YOU HAVE A REASISTIC REASON WITH SOME TECHNICAL PROOF OF WHY IT'S BAD I WILL BE HAPPY TOO TRY AND GET THAT TOO SOMEBODY
it's bad is not going too cut it with me. i want a deeper response than the threads will rip out. i can't go to anybody with that because ford uses locktite on many aluminum threads without a problem during service and i will look like a fool asking that.
bring me proof that this will happen.
tonight alone at work i removed 6 botls from a steering knuckle that was locktited into aluminum threads and they went back in no problems.
how about steering racks. the aluminum threads that the inner tie rods attach too are coated with red locktite from the factory and i have replaced many inner tie rods without damage to the threads.
how about brake caliper bracket attaching bolts. all locktited in from the factory. into aluminum on some cars.
i understand the threads for this plug is a lot smaller but i still don't see how you could tear them free.
and the other reason listed that the loctite itself will cause the plug too blow out is just laughable. even if you used low temp loctite and it melted away all you would loose is the protection the locktite offered.
bill if the plug became fully unthreaded then the damage would not be as severe.
what happens is the plug loosens slightly. and then it starts too rock around in it's threads. some have heard ticking or what sounds like a exhaust leak right before the plug lets go. the coil on top of it bolted in prevents it from unthreading any further so it stays slightly backed out and i think we can all agree that a loose threaded joint is not very strong and will vibrate and tear itself apart.
after awile what happens is the plug rocking around loose in it's threads causes extreme metal fatigue to the threads too the point where cylinder presure will sheer the damaged metal away and blow the plug and coil off.
plugs back out slightly on other motors too but most heads can survive it. but the 5.4 and some early 4.6's had only a few threads and the added stress of not being fully touqed down is too much for the thread to handle.
the use of loctite prevents this backing out of the plug.
some people have found loose plugs with as little as 5k miles on there car.
one of the guys at my work has a harley davidson 5.4 S/C he had 5 plugs loose when he first checked them ( not sure of the mileage) he was very lucky he caught it in time.
a fully secured plug will not blow out of a modular motor head it's when they back out and the threads get damaged thats when they blow out.
(slang there! no need to alert the local constabulary!)
And, I never said I know anything about cars. That's why I take my car to someone who does. And, I don't think he ever uses Loctite on the spark plugs. 
