That is aweful high compression. Last motor I ran that had that much compression ended up busting ring lands out of two pistons(they were cheap cast pistons) and wasted the rod bearings. I never heard any detonation but apparently it was happening. These days I shoot for around 175-185. No more. I agree with compression that high I would be running some 110 mix untilI could do something about it. Think of it like this... when the piston travels up on the compression stroke the higher the compression is, the more it's trying to push the piston back down against the pressure buildup. The rod bearings(mostly the rod side) are the wear parts that take all the heat of the action.