(How do you import two photos into a post???)

I was worried that #3 spark plug hole was stripped when I took out the plug.  Very tight with a ratchety vibration all the way out.  I could actually hear a high pitched vibration.

I first used the AMPRO thread chaser from Auto Zone, on plug hole #2, with known good threads, to get a feel. It kept hanging up. Granted there was a lot of crud on the spark plug threads, I didn't like it.  Besides that, it wasn't long enough to get to the bottom 3-4 threads.  The thread chaser looked crude, rolled threads, vs. cut threads.  

The fix: I cleaned the spark plug threads with an old T-shirt soaked with carb cleaner wrapped around a screwdriver, alternating 3 to 4 times with a good, well cleaned used spark plug sprayed with PB Blaster to act as a lube and help loosen the crud.  It appears that #3 SP hole was just over loaded with crud, not stripped.  I got the holes clean enough to seat the spark plug with little effort.

Photo:
Right, spark plug thread chaser.  This was junk, imo. 

Left, old #3 plug.  Note the clean bottom 3 and top 5 threads.  I thought that was the result of a cleaning action caused by threads stripping in the aluminum spark plug hole.     

Center, Bosch Platinum #4216. 

Where is the center electrode? 
Maybe it's that little spec hidden in the insulator.  I guess they can't give you too much platinum for $2.25.
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Tom F '95 945, lein holder on a '95-944Ti, & RIP '78-245