If you do some Internet research on using or not using a heated intake you'll quickly find a LOT of varying opinions on the subject much like anything else related to this hobby.
I highly recommend using the heat crossover in the intake if it is in place. There are really no negatives from doing so, unless possibly if you lived on the equator and it never got below 80 degrees outside.
A working crossover in the intake provides many advantages, and blocking one off or not using it just delays heating up the intake as it will heat soak eventually anyhow.
The intake needs to be hot to keep fuel from "globbing" up on the walls and requiring a much richer mixture to make the engine happy with a wet flow system.
Folks claim "vapor lock" and other problems with having one, but the carburetor, especially a Q-jet has high velocity air coming down thru it for cooling, and most factory gaskets between the carb and intake act as insulators to keep the fuel from boiling in the bowl.
For operation in sub-freezing temperatures the crossover really helps to prevent freezing/icing and makes for much greater efficiency and much faster warm-ups.......Cliff