Why are my distributor cap terminals burnt?

It runs great, up until 3400 RPM or so. With 22* initial, I’m at about 44-46 total at 3400. So I think I have too much timing and it’s detonating.

The plan was to install the limiting plate to keep me around 36-38, but this damn distributor won’t work. I’ve got the distributor back together now, so I’m going to dial back the initial to see if that helps.