I don't know if it's the jetting, the timing, the chamber design, or what... but that's not what I'd consider a good burn pattern. My understanding -- and it's pretty limited -- is you "should" see a more complete burn across the quench area and more uniform coloration of the chamber.

These pics aren't ideal, but show the burn pattern for this head & piston combo is spread out more. This is either a .040" or .045" quench height and the heads were pulled after about 25+ pulls on an engine dyno. Jetting was still being worked out, but tended towards the lean side. Ignition timing was 37*, IIRC. Fuel was a 50/50 blend of 110 leaded and 93 E10 unleaded.