I tried to remove the spark plugs last night. These may well be the original plugs (35k mi. on car) They are very tight and after breaking them loose, turn very hard.
I'm worried about destroying the threads if I continue to try to force them out.
Would warming the engine up and trying again do any good or, would the plug threads just expand at the same rate as the housing?
Any other suggestions?
Thanks for your help

 

After a whole day of working it in and out spraying with PB, I finally got one plug out.

Turns out that they are NKG SD10As, which if my limited research is correct,
were original to at least '86 & '87 model years.

Tomorrow, plug 2.

 

If you can turn them a "touch" at all,I would spray them with Penetrating lube..like Seafoam deep clean..Turn them back in,and work them out and in until they feel good enough tto take out freely.

 

Thanks for that Styx!
As I said, PB Blaster and in and out over the course of a day did the trick.
Against the advice of NKG, I think I'll use some Felpro C5A when I replace the plugs.
I can't tell you how nervous I was yanking on the ratchet to get the first one out.
Tomorrow....plug #2!

 

I found changing the plugs was a nightmare in mine. Not the worst ever but not easy

 

I made a Mistake.
the Stuff I meant to say is: Sea Foam DEEP CREEP.
I recently started using it and I found the stuff phenomenal!

 

Aside from the fight getting the plugs to turn, it was not as bad as getting to the rear plugs on some transversely mounted engines.
I did move the plug wire bundle out of the way and that made it easier.
I'm going to try the Sea Foam stuff. If it's as good as the rest of their products, I'll switch to it.
For now, PB Blaster is my go to.

 

Aaannnnd, don't forget to put some anti-seize on the NEW spark plug threads before installing them! -I do (permatex anti-seize lube "advanced formula"), works like a charm...EVERY time!

 

Be careful with the anti seize.
Ngk put out a article advising not to use anti seize.
It causes inaccurate torque readings either by hand or torque wrench, which has caused them to break the plug in half leaving the threads in the block