Worrisome spark plug port

[Whidbey Goblin]

I changed the plugs in my motor today and when I got to what I believe is cylinder number two the plug came out with RTV. Pretty weird. Upon inspection the seat is not flat like the rest. It has a sharp raised portion that wants to cut into the interior of the washer on the spark plug and doesn’t seem to seat well. Has anyone seen this? It’s probably really hard to tell in the pictures. One picture is of a normal plug seat and one is the (greasier) plug seat in question. Any motor gurus that know what I’m talking about and can lend some guidance?

 

[Ross]

So you are saying the red dotted circle is raised up a bit higher than the flat washer surface?
The spark plug threads are okay?

Spark plugs can have different thread profiles. I wonder if cylinder #2 has had a few different brands of spark plugs put in it, and some of them have pushed up that little ridge at the seal.
If the ridge is small enough to be absorbed in the crush washer on the spark plug, then I would just put a new spark plug in it, and torque it down.
If that doesn't fix it, try a different crush washer.
If that doesn't fix it, I would try to grind down the ridge. Maybe glue a Dremel cut off wheel on the bottom of a wooden dowel, and spin it back and forth by hand. It will drop grindings into the cylinder, so you might want to plug the hole with a paper wad, and vacuum or pick it out later.

 

[Lonny]

It may have had a thread insert installed once upon a time. Make sure you properly tighten the replacement spark plug to the manufacturer's torque spec.

The crush washers on sparkplugs are usually pretty forgiving, it will try to conform to whatever the seat is shaped like.

Replacing the sparkplug with an RTV sealer will not likely damage the engine but it will not stop the plug from leaking. Combustion pressure and heat would find their way through RTV the first time you fired the engine.