Ok well as the title says it's a question about spark plugs actuall just one spark plug. Ok so here goes the story. I was up until three a.m this morning changing out the spark plugs and the first eight went fine, I started on the drivers side and worked my way back Changing out the plugs and boots and then went to passenger side and the first two went fine then got to the third one back and pulled the c.o.p well the boot stayed on the plug so I grabbed a pair of pliers and started pulling the boot off that thing was stuck in there like somebody glued it in or something. Bad sign... Then I grabbed my 5/8 spark plug socket and tried to pull the plug.... Well that's weird the socket doesn't fit so I grab a 9/16 socket and it fits so I pull the plug and out comes an autoliite ht1 plug I thought that was kind of weird because all the others so far had been motor craft plugs. Oh well I put in the new plug and try to torque it down and it doesn't tighten down, pull it back out and look at the threads and there are aluminum threads on the spark plug😁 so I look at the plug that came out and the threads on it start off the same size as the standard plug but they slowly get bigger so I had to put that one back in. What a frustrating thing to do at two in the morning. So my question is is this just a band aid plug that somebody put in there or what? I've put about 25,000 miles on it since we got it.

 

I don't know how this plug could be used in an Excursion

https://www.amazon.com/Autolite-HT1-...ype=automotive

 

Sounds like a band aid to me.
Ours blew the #3 plug at 108k - factory Motorcraft plugs.
The #3 plug blowing seems to happen more than others.
You'll need to determine the size of the hole left in the head after the incorrect plug was forced in.
I used a Time Sert kit to install a new threaded insert for the correct Motorcraft SP479.
Time Sert has different inserts for different size holes to be repaired.
Might contact them to see what they recommend.
With any kit be absolutely sure the piston is down and the valves are closed before tapping the hole.

 

we've put 23,000 miles onto it this way with no issues, I guess it's just a matter of time till it blows against

 

I believe the Dorman kits use those plugs.