When riding my spark plug and coil popped out. I tried to screw the spark plug back in but it just spins. Has anyone ever had this problem? I'm thinking of re-threading it.

Helicoil 5334-14 Save-A-Thread Thread Repair Kit M14 x 1.25
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i have used the thread inserts that u can get at any auto supply store.
some have a shoulder on top. make sure u set the shoulder down into the head or the plugs can pull the threads out when u remove the plug.
if u are VERY PATIANT, u can do it without removing the head. place the piston at tdc. put grease on the tap. start to tap, then remove the tap. the alum shavings will stick to the grease. just keep repeating until done. if u get a few filings dropped in. u can put a dab of grease on a screwdriver tip and pick it out. when u are done blow it out with compressed air.

 

Probably didn't have the spark plug tight. Ford had an issue with their F150s coming from the factory with under-torqued spark plugs. As the cylinder fires it puts pressure on the plug trying to push it out the hole causing the plug to rotate ever so slightly and hammer the threads. 5K miles later, pop, the plug rips out the threads and won't go back in without a repair to the head.

Need to heli-coil it. Take the head off, drill and tap the hole for the heli-coil, then reinstall. It's a fairly simple process (5mins of repair for several hours of disassemble). You COULD do it with the head on but you risk getting aluminum chips in the cylinder.