yr right, you've obviously spent a lot of your time spannering with aero engines, but that's not the same thing as playing with the parameters as they run on a dyno.
There really is such a thing as light detonation (I prefer to use the term knock) and indeed when you run a cylinder pressure transducer, you can do lots of maths with the result to calculate a Knock Intensity (KI) number that is a unit-less scale of how much knock is occurring. Auto engines are tuned to run right on the borderline of knock, whereas the FAA mandates that aero engines run so far away from the knock limit (at rated power) that everything carbons up and goes smeggy, not to mention the outrageous fuel consumption.
As far as exhaust valve temperatures go, they correlate more closely with cylinder head temperature than exhaust gas temperature because they spend most of their time seated and gas flowing past them at 1-2Bar or so is not a very good heat transfer mechanism. The key point is that cylinder heat temperatures are the most important long-term indicator of cylinder and exhaust valve/seat life.
Oh, and knock begins at the coolest part of the combustion chamber - not the hottest as is generally believed. I can explain why, but not in a few words.