The plug was ‘nice and gray’? Not sure I ever want to see a ‘gray’ plug when I come in. I prefer a very light (REALLY LIGHT) brown to tell me there’s plenty of lubrication going on.
Where physically are you racing? What temperature was it outside? What was the barometer?
As you can see from the piston, the ring actually snagged the port and broke off part of the dome, but apparently not before enough heat was generated to burn that hole in the backside.
Looks to me like there’s multiple scars on the piston as well, as if it got too lean before, but didn’t get so lean that it burned up.
Gray plugs…not good. That’s usually ‘gray’ aluminum coating the electrode.
