@Mustangman has good advice.
The plug tip is just a little longer than the hole that it goes in and because a few threads protrude on the cylinder side of the head…they tend to get carboned up.
Then when you remove the plug the carbon tears the threads right out of the head as you remove it.
If you are lucky, the carbon will get sheared off the threads asx you remove the plug. Then you might have enough thread in the head to snug the new plugs.
My nephew has the 4.6 and someone stripped the threads on 4 of the eight plug holes.
I had to install inserts in each one. When the previous owner changed the plugs, there was just enough threads to barely snug the plugs again. Then a few months passed and my nephew started blowing plugs out.
When the plug does blow out…the force tries to push the coil out of the way ,and it tears off the ear that holds the coil down.
So you need to buy new coils for each plug that blows too.
Yosemite