Black spark plug ooze

[doug.nichols]

Well, I took "Trudy" on her first road trip since I have owned her. Just 15 miles. She did great. Lots of hills here on Orcas Island, WA, but I never went over 30 mph. When I got home I popped the hood and noticed that some black liquid appeared to be leaking from the number 2 and number 4 plugs. See the two picture attached. Does anyone know what this substance might be and what could cause this?

Also, Trudy sounds like she has a know at modest rpms from time to time. I realize that is not much background on which to base an assessment, but cans someone tell me what would be the most common source of such knock? I have never had the engine apart.

Thanks,