Need advice on removing a stuck spark plug

When replacing the spark plugs on my 87 F150 with 4.9 liter straight six, I could not remove number five plug. Using a standard length (10" or so) ratchet, I could unloosen it a couple of turns with difficulty, but then it became too difficult to turn any further. Rather than risk breaking it, I gave up and retightened the plug. I just purchased the truck about one year ago, so I don't know much of the past history of the truck. The other 5 plugs came out without difficulty.

Is this a problem with this engine? Any suggestions for getting the spark plug out?

Thanks,

Tim Kirby

I have seen plugs that didn't want to come out because they had carbon on the threads right near the end (towards combustion chamber). I screwed them back in a bit, put penetrating oil on the exposed threads, waited, then screwed the plug in and out, a little further each time, rather than just muscle it out. May want to use a spark-plug tap to chase the threads in the head before new plug goes in.

I have no personal knowledge on the 300-6, but we have some knowledgable folks on this engine on the Late Bronco board. I'm sure they read this board too, so maybe they can tell you if this is common on this engine, and if they know a better way to get that plug out.
UncleDon

I know of no problems with the 6 engine plugs. I agree with UncleDon, it is carbon on the threads, and his removal approach is correct.
Good Luck,
Rick-