I’ve been having some vapor lock issues on anything resembling a warm day. I get a little bit of stumble in motion, but it’s mostly heat soak related fuel boil/vaporization.
The phenolic spacer seems like a good idea to prevent heat conduction, but the Q-Jet carb gasket is pretty thick, and I question how much real world improvement would be yielded there. I’m trying ethanol free 87 and seeing how much improvement I get there. Ethanol’s boiling point is considerably lower than pure gas. Plus, my system predates factory return on GM passenger cars even though I have A/C and use it religiously so I’m already at a loss there.
If I’m unsuccessful, I might look into making a carb blower fan that has access to ambient air via the Thermac. It’d be relatively easy in a square that has fresh air access courtesy of a duct, not as much a car whose snorkel sits under the hood. MG and Toyota, IIRC, toyed with carb fans back in the day, but their setup is carb proximal, about where your dashpot would sit and sources air from well inside the engine bay. GM tried one on F Bodies, but it sat on the fender, had independent ducting, and ran from a constant hot through a temp switch to try and cool the carb down to 165*. External booster pumps have seen some success in the mid-80s P30 based motorhomes, but in-tank booster pumps were more reliable at the tail end of carburetion.
GM did a bunch of vapor lock related service bulletins targeted towards F Bodies, but they apply directly to B and G Bodies and indirectly to and I need to go back peruse those closely. To anyone interested, I would suggest checking those out.
https://www.thirdgen.org/forums/carburetors/320143-vapor-lock-bulletins.html
