I have noticed that by using a fan on the endbell it reduces the heat generated considerably. More so than just a plain heat sink on the can. The endbell copper draws immense amounts of heat generated by the brushes onto the comm. I run Epic stock, CO27, and Monster using the fan keeps them much cooler than without. Unfortunately I don't have a tempgun to get exact measurements, but to touch its way cooler. I use a Sunon 7.2v fan.