i know a thousanth dosent sound like much but when you start messing with it and ther is already a very small ammount between the piston and the head it is alot. im not saying dont experiment, that is great, but i would make some bigger cooling fins or more fins to get rid of some of that heat. the reason i say it might have pre detonation is cuz it is running hot, but also the more compression you have the hotter it runs.....