Carb Fuel Evaporation?

Actually if you are using an electric pump, I would NOT plan on "not running" it at times. Either run an electric through a mechanical and always run it powered or get rid of the mechanical pump

Part of the problems with modern fuel is that it boils more easily.

Boiling point is partially determined by PRESSURE, and when using "only" a mechanical pump it is bad enough.........the pump being up front causes a low pressure in the tank to pump line just because of physics, and this alone somewhat lowers the fuel boiling point.

Now, if you come along and add an UNpowered pump, you add more restriction.......which causes the mech. pump to further lower line pressure, and further lowers boiling point

My car is STILL torn apart. But before I went to EFI, the smartest things I did was --convert to electric pump, -- build a fuel return system using an orifice equipped Wix filter,---and use a carb thick insulator spacer.

"It might be" that Edelbrock carbs are somewhat worse for fuel boiling/ evap because the bowls are right down on the manifold, effectively.