I agree with everything jerry has said. TO properly set up you cyl and head you need to know the installed CC at TDC. This allows you to calculate Static and more importantly Trapped comp ratio. From there a couple assumptions need to be made on the Dynamic Ratio of the Engine. It would also help to know if your issue is actualy detonation or a overheating issue. I would guess without being able to look at it, its a combination of both.
Have you looked at your head off the cylinder? if so is there step machined into the Squish band? If there is, your looking at a new dome or Blank to get you where you need to be for Squish. If not The head gasket will need to be eliminated or the top of the cylinder machined to get proper squish.
Have you tried a better fuel, like C12 or C14 to see if its a detonation issue? also a couple sizes up on the main will cool the mixture and could point you to a detonation preignition issue.