in addition, aluminum also expands more than steel.

 

I tried to remove mine with the engine cold per Ford's instructions but couldn't break them loose. Ran the engine just a few minutes to just warm the heads a bit and then I was able to break them loose.
I've been seeing posts lately talking about using an impact. That scares me. Man I could see pulling the threads out of the head with an impact.

 

I saw that! i would never use a impact gun to do spark plugs!!

 

that'd be like flushing out your engine with a garden hose...

 

Lol, yeah, dont' be 'That' guy. I wish I could find the thread