[olddog]

Well finally my question has been answered.

The question: Why is it that the timing is only increased until 3000 rpm give or take a 1000 or so?

Experts (so called) have always explained that as the rpm increases there is less time to burn the fuel, so the timing must be advanced as the rpm increases. Some of these experts state that the burn rate of the fuel does not change, with rpm.

I have always said there is more to it than less time to burn the fuel, or you would need to keep advancing the timing all the way up the rpm band. I also calculated the time difference with respect to rpm and the advance curve does not keep up with the loss of time.

Finally someone explained it. The burn rate of the fuel is increasing with rpm do to the increase in mixing with rpm. The burn rate is NOT constant, with respect to rpm!