Originally Posted by EAnton
An increase in the number of threads is proof that the heads have been changed. Ford may not acknowledge the change but that doesn't make it a fiction. They apparently have increased the number of threads in the spark plug holes on later (2003+?) heads.
A higher number of threads on the spark plug doesn't mean the heads were changed.
Just checked, the 6.8L heads are the same part # for 2000 through 2004.
The 5.4L heads are the same part # from 2002 through 2004.
Still haven't heard from anyone who can definitely say there is a redesign at any point.
I still say, if Ford would change the maintenance schedule to include cleaning/re-torquing the spark plugs every 20K we'd never have heard of this.