ORIGINAL: Sport_Pilot
There is no problem with overheating on glow fuel, unless you are using high nitro fuel. The problem is lack of lubrication with lean fuel mixtures. If you convert them to gas they will operate at much higher temps without any problems, except perhaps a few with small fin areas.
There are perhaps a few exceptions to the above. For example a Fox Stunt .35 may overheat with a lean run with moderate nitro because of its very small fin area.
I have to ask, in our glow engines isn't lubrication failure of the piston to cylinder seal a direct response to over heating?
Now the FAI F3D and AMA Formula I pylon engine have been known to actually melt holes in the piston tops[X(][:@]. But these are extreme cases of engine abuse at elevated temperatures (lean mixture settings). The two mentioned pylon engine are at the extreme nitro ranges, zero for the FAI engine and 65%+ for the Formula I engine. Nether engine will survive long without a close fitting pressure cowl.
All the best,
Konrad