I am driving my son's '08 F150 4.6 and it has blown a plug. The plug's last couple of threads were messed up and I was hoping only the same was true for the head. I thought I would try chasing and tapping the threads first before attempting a more permanent repair. I have run a 14x1.25 tap through the spark plug well several times and can do so using only my fingers (with the appropriate extensions). My question is: With the tap going through so easily, why can I not get the new spark plug to go in past the first thread? I am doing it all by feel since you can't see down the well and do not want to force it.
PS. Thanks to all who made it so that I could start this thread in the first place.