Carl,
You are correct when you get carbon fouling. Black soot and powdery. Cylinder heat while idling without all the fuel being used will cause a light black glazing on the plugs...slight powdering. Check the Autolite spark plug reading guide. This 216 is not a fresh rebuild. Has 51,000 and some change. Was running great until I changed the oil last week? After I changed the oil it began to misfire after idling for 30 minutes or more.
Jerry,
Thank you for chiming in! JQI sounds like that may be my whole situation. I have 2 sets of new plugs as stand by. Will let you know how it goes. Do you know if AC Delco makes a hotter plug than the R45S just to use while tuning...not driving. Should I turn the idle mixture screw in on the carburetor, say to 3/4 turns from seated? Set at 1 1/4 turns now.
