I guess I should elaborate on the detonation, those ridges beside the exhaust valve look like the worst offenders, they are gonna get real hot real fast as well as blocking flow of the last little bit of exhaust stroke and that will reduce scavenging. I would eliminate them all together. Then open up the spark plug divots for more access for the flame to travel to all surfaces faster and easier then put a big radius on everything else except above the top ring land obviously. I bet you will make more power and reliability even if it costs 1/2 point compression.