Edit - actually I'd just buy a high quality square fluted extractor, like Champion suggests below. Too risky otherwise and apparently it can take a lot of torque to break it free.

I'd buy one of these chisel sets, sharpen up the edges on the best choice so they bite better, tap it in the hole and twist. It will probably screw right out.

https://www.harborfreight.com/12-pie...set-66337.html

 

I knew that I had seen this type of failure before and finally found a couple of links on the web. Champion has recommendations.

Take pictures when you get it out. And, what brand? So people can avoid it in the future.

https://www.championautoparts.com/Te...park-Plug.html

Here's a thread with a picture of a real plug. It's an NGK. Post #17.

https://www.k20a.org/threads/spark-p...process.68609/

 

I'd suggest reviewing this older thread over at FTE: https://www.ford-trucks.com/forums/1...park-plug.html One of the posters pretty much gives the same advice as does the Champion tech note that BBXL linked to.

It would likely help tremendously if the OP would show us the remnants of the original plug that failed that he's recovered That would give a better idea of what's left in the head.

 

I too would like to see what the other plugs look like, I'm even guessing, there was either, A, no anti-seize used when installed, and the mfg of the plugs did not say, "Do not use anti-seize.......", in short, should have used anti-seize. B, the plug was cross threaded and Over torqued at the same time.

 

More likely, it was simply neglected for too long or water got into the plug well and rusted.

Since the OP has been sparse on details and completely devoid of history, it's probably just musing on our part at this point.

 

Rust is a powerful drug. I would suggest, take the head off, take it to a good automotive machine shop, and have it taken care of, right the first time. If the other plugs don't budge, I'll go with the **** poor maintenace, rust theory. If the others come out with normal effort, I'm going with the cross thread, over torque theory. But as you have pointed out, all of us are shooting in the dark. In the end, I hope he is able to fix it, and get his truck back on the road.

 

To try and not leave you guys in the dark.. I traded a 2005 Pontiac G6 for my 2010 F-150. When I traded for the truck the head already had the issue with the spark plug. So now im fighting to get this thing fixed... Had some family emergencies happen which paused the process of trying to fix this thing. I confirmed with a magnet that infact something steel is still in the head. I believe it was the threads of the plug as nothing else could possibly cause this issue. I purchased the calvan kit to attempt to retap the head and no beans cause it wont cut the aluminum due to probably the threads still being in the head.. I tried an ez out no beans.. Im now getting to the point of possibly removing the head but dont have the tools to get to doing it just yet.. Gotta get a harmonic balancer remover etc. If anyone has any idea ill take any. As for the other plugs theyre all in good condition no rust nada. Also as someone asked before they are the motorcraft plugs which only the one broke in the head I believe it to be the previous owner not installing correctly..

 

My thought is you are correct, cross threaded, then WAY over torqued, pull that dude, take it to a good automotive machine shop-it won't be the first time they've seen this. Best of luck to you.

 

Did you try the "Square Cut Easy Out" shown in the attachment to Post #22? At this point, I would try this before going through the work of pulling the heads, the square cut may work. I doubt the plug was cross threaded since there is very little room in the spark plug recess to get the socket out of alignment. Make sure the piston is down and out of the way of the square cut easy out if you do try this.
Question - Assuming you used a round easy out were you able the get a good bite?

 

Adding....

Make sure the piston is down AND THE VALVES ARE CLOSED.

Don't want to make new problems that are avoidable.