I noticed when I pulled my 392K head that the exhaust seats were fairly scorched and a few of the stems had galled.

Back in the day we used exhaust valve rotators to eliminate hot spots and keep the valves and guides wearing evenly.

Makes me wonder if my heads would not have cracked around the exhaust ports if the heat was being dissipated properly.

It would be smart to use them, but I haven't yet found a source.

 

Police interceptor engines of the 70's had them, helped with prolonged idling from burning valves.