While studying for something else, I found these if some are interested.
http://ntrs.nasa.gov/archive/nasa/ca...9930081891.pdf
and
http://ntrs.nasa.gov/archive/nasa/ca...9930091891.pdf
you can find everything from NACA on exhaust valves
here
The former has a chart showing CHT, exhaust valve temperature, while mixture is varied and power held constant, Figure 8. It also has EGT (though not enough data points to see the peak properly) the significance of the graph is that’s its at a constant power. The engine is watercooled.
Its reinforced that while some of the OWT may be tales, some of the POH leaning procedures for these old aircraft is still appropriate, YMMV.
I still agree for updated engine i.e. appropriate instrumentation and fuel delivery, different leaning procedures would be appropriate.
The later report has a method of calculating the valve temperatures, but its not a simple read...