Need help with missfire under load on 340

Pulled all the plugs and you can tell its running rich which is no surprise because it always has, but i noticed that the plug from number 1 had a crack on both sides. I split the porcelain off where it was split and it looks clean, no carbon tracking.

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with the porcelain split like that if it was arcing to the head i should of seen a carbon track correct? Or was it just dissipating the spark in the boot? I dont think i did it taking it out