O.K. Thanks for all the replies, even though I'm more confused now than when I asked the question! LOL. I guess what I was trying to get at was. How hot is too hot. I realize two indentical engines running at their best performance could run at different temps. But all these engines are basically built out of the same materials. (I think). So, I'm guessing that they will be damaged when they reach a certain temperature. I'm not looking for the magic number. I just want to know if it's 200*F, 300*F, 500*F, or 1000*F.