From other experience oils in the combustion chamber start to break down above 450 F. The head and cylinder will be a much lower temperature than the combustion area. One of my friends shoots the temperature at the base of the cylinder and uses 220 F to 250 F as a guide while the engine is running. If the temperature goes up rapidly on throttle up or idle something is probably wrong.

Temperature measurement when used with caution could be a good tuning tool but most tend to reject the possibilities and very little data exists.

Bill