Spark plug melt down

The Oily Bits S1 Specific Topics
1

Do you think this cylinder was running a bit on the lean side?
Melted plug

Looks like the valve seats didn’t survive the meltdown, only 90psi on that cylinder on a compression test, the other three cylinders and plugs were fine.
I had a problem with the threads on that cylinder the last time I pulled the plugs. Had to chase the spark plug hole with a thread tap. Planned on a proper fix this winter when I was to take the head off and possibly send it to DVA.
The plug was loose when I pulled it, so I’m thinking that it was sucking air in on the intake stroke leaning out the mix. I already run the engine on the lean side to get the max out of the old girl but use 108 octane leaded race fuel to compensate.

2

Just a little bit!

3

OUCH!

4

what does the piston look like

5

Don’t know? I put a new plug in and I’m continuing to track the car until the end of the season.
A compression test after the melt down yeilded 90psi on that cylinder, but the car still seems to be running strong (for now).
I only have a few more track events before I pull it apart for a winter rebiuld, we’ll see then what surprises lurk under the head.