Thread: Sooty spark plug, only one

Ever since I got my XP, I've noticed the #3 spark plug threads are black along the full lenght of the threads. None or the other plugs are like that. It baffles me how exhaust soot could completely cover the spark plug threads that should be in the threaded part of the heads.

Any ideas?

clean the threads out. I would look for any exhaust leaks from the TOG's...

if not.....you may have some blow by.....

Originally Posted by UR LOSN

clean the threads out. I would look for any exhaust leaks from the TOG's...

if not.....you may have some blow by.....

If the TOG's were leaking there wouldn't there be black on the outside of the plug? The black is only on the threads but it is completely covered. Just as if you taped off the rest of the plug and spray painted the threaded portion.

Originally Posted by Reptile

It could be that the plug isn't seating in the head all the way. Not to poke at you or anything, but changing plugs constantly may be wearing the threads out.

I guess it's possible, but surely not on iron heads and only one plug.

Originally Posted by Reptile

I've seen many times where the threads get pulled in heads. It's not really that common in cast iron as opposed to aluminum where it happens 90% of the time.

That's why using a type of anti-sieze will help lubricate the threads to keep the plug from grinding away at the cast iron.

Interesting thought. And I was so careful making sure the area was free of debris, and only snugging the plugs. Out of all of the cars I've owned and changed plugs on, I've never seen this happen. Even the motorcycles with the aluminum heads.

thats a good point about the threads. I didnt think of that.

Some of the cars/trucks I've owned, where old high milage that used the plugs with a short life. You know the kind, backin the day, when some people would clean and reuse the plugs. The removal and reinstallation of plugs on those engine had to be multiple times greater that on my 55k mile 04. That said, how to you correct this issue? New ported heads? Yes? Good ,I need to go sell this to the wife.

Seriously though, I've been looking at these plugs and noticed the black powder residue is a lot thicker on the leading two CC threads, that all of the other plugs.