Comments on my 340 plug under mag

Who cares what the total timing is. What is the timing at peak torque? That plug shows signs of distress for sure, but it ain’t the total timing that’s causing it. And with no full throttle, full load pulls reading the plug for fueling is useless. Looking at the plug, it’s detonating, it’s cold, and the total timing is a degree short of perfect. You need to work on the CURVE and get the timing out of it when it’s rattling. You might need to move to more octane in the short term just to keep it alive.