Evaporating Fuel in Carter 4-Barrel Carb?

retractable said

I am able to get 92 octane with out ethanol here in Minnesota and is available at many stations. I still have the carb problems when I run the 92 octane only.

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OK, Mines a 67 273 2brl. I had a see through filter at OEM horizontal location, atop the intake. Always a air bubble in there, plus after the engine was hot I could watch the filter fill and empty repeatedly. That's why the idle wasn't consistent too. It took me a little while to finger out that empty wasn't empty. What I was seeing was fuel vapor flowing backward from the carb bowl. Confirmed the bowl vent was open. How the heck there could be more vapor pressure than would escape through that vent is still a mystery. Anyway...
The thicker base gasket and relocating the filter ( changed it to a metal type also ) cured it.
I did need to alter the choke rod height to compensate for the changed carb height .