There is no standard. The surface of the engine part anodized, polished or grit blasted at will change the reading from your infrared thermometer. Your best bet is to set the engine for a bout 300 rpm down from peak on the rich side. Measure your best performance (time). Then make your reading. use this as a reference point for future tuning. If you want one of the best cooling system to control heat build up try a pressure cowl. You will often see these on high performance set ups.

Your best tools are still the tachometer and stop watch!

Friends don't let friends fly nickel,
Konrad