I would first try carefully threading a new plug in place and see if it will torque to 13 ft-lbs. If you do have to resort to one of the heli coil kits, PULL THE HEAD to do it. Don't let the chips in the engine.
To prevent this from happening in the future, when changing plugs ALWAYS:
o always, Always, ALWAYS remove plugs when the engine is COLD! You can probably get by with an hour of cool down time, but overnight is MUCH better.
o Blow out spark plug wells with compressed air before removing plugs.
o If you choose to use anti sieze, ONLY use Copper based and use VERY small quantity on the THREADS ONLY. Do not allow it to get on the plug below the threads.
o Torque the new plugs to 13 foot pounds! Before aluminum head engines, I NEVER used a torque wrench on spark plugs, but that was then, this is now!
That's what I used. Still OK 2+ years later. There is no need to remove the head if you or your mechanic follow the instructions (gobs of grease to trap the shavings).
That's what I used. Still OK 2+ years later. There is no need to remove the head if you or your mechanic follow the instructions (gobs of grease to trap the shavings).
The Timeserts are a very good product and work much better than heli-coils in my opinion.
Don't forget the dielectric grease inside your COP.
Every Ford service/warranty consultant I have ever talked to has said the notion of not removing the plugs from a warm aluminium cylinder head was merely a legal discalimer on their part that surfaced once the blown spark plugs started to become more prevalent. At normal operating temps an aluminum cylinder head on these motors only gets up to about 180-190° F max. That isn't anywhere close enough to somehow soften the spark plug threads or create any type of thermal expansion on a scale that would prove to be damaging to the spark plug threads if the spark plug were to be removed correctly while the motor was warm. The 13 ft-lbs is also a legal disclaimer that Ford came up with in an effort to cover their ass from any pending lawsuits regarding spark plug blow out. Not that the 13 ft-lbs is wrong, but there is absolutely no need to put a torque wrench on a spark plug. BTW, exlcuding high end and expensive digital torque wrenches, most lb-ft torque wrenches out there don't read very accurately under 20 ft-lbs. If you really feel the need to use a torque wrench on a spark plug, you need to use an inch-pound torque wrench. Excluding any Ford techs that may now be required to use a torque wrench on plugs, if someone can't closely estimate by the feel by their hand how tight to get a plug, they probably don't belong under the hood of a car.
There are lots of 4.6 guys out there out the drag strips and AutoX tracks that change plugs all the time when the motor is warm (including us) with absolutely no problems. The problem is that it is very easy to cross-thread a plug on an aluminum head, and some people won't even relaize that they have done it. And once it has been cross-threaded, it is just a matter of time before the plug threads are damaged enough to allow the spark plug to push the ejection button.