Insulating Against Heat on the Carb

BrianT said

Another thing that we haven't addressed is what about the make up of the fuel is causing it to evaporate out of the bowls. At least around here, it is made up of 10% ethanol. If I run the expensive premium with NO ethanol, the situation improves.

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Yes, I have. The insulating spacers address the conducted heat only. The large plate type insulator that I've suggested several times address' the heat radiated off the engine below the carb. A spacer won't do a lot for the radiated heat, and a plate can only do so much for the conducted heat (acts as a heat sink). A combo of both is the best route forward. Plate on the intake, then the spacer.

FWIW I looked up some thermal conductances:
Phenolic (linen filled): 3.75-4.03 BTU-in/hr-ft^2-°F
Birch: 1.20 BTU-in/hr-ft^2-°F
A356 (Cast Aluminum): 1050 BTU-in/hr-ft^2-°F

Note that the wood spacers aren't pure wood, they have some sort of resin put into them under high pressure so a wood spacer is likely closer to the phenolic number than the straight Birch number. Could not find a number for paper, suspect that it is similar to wood.