Head Temperature Old School!

Just thought of something I used a long time ago on my Harley. It was a Ultra Classic with a side car, geared for sidecar, carbed, cammed and piped and would run 70-80 with ease. Had an oil cooler, switched to synthetic oil and tyranny fluid do to Yuma AZ heat.

The Harley dealer was into building his own planes. Was on his second. Jim was his name, just a cool old gear head that had a small Harley shop on the border of Mexico. Full machine shop too.

So he says why don't we watch the head temperatures? I say? He says theres head temperature gauges in the air plane magazines that are just run under spark plug. So he gets me one gauge with two sweeping handles! So we had both cylinders on one gauge.

Now I know this was air cooled stuff but could these gauges lead to optimum cylinder temperatures? Isn't a key goal on timing watching Exhaust Gas Temperatures? Could they be correlated?

i don't know about optimum head temps, but it would give you a good idea of if you're running too close to the limit of your head's casted material. i think aluminum starts melting around 900*F?

i'm fairly certain EGTs and head temps will rise and fall in similar situations, just the rate at which they do so may be different.

6061 melts around 1100 degrees. HOWEVER, being a welder, I can tell you that a large thick chunk of aluminum will take quite a few seconds to form a puddle even with a 200 amp Tig torch pushing a 3000+ degree arc into it. So even a 1/4" thick combustion chamber with water running on the other side will transfer a LOT of heat out, without melting.