Why do you need heat in the intake manifold?
The so called 'hot spot' underneath the carburetor is designed into all chevy/gmc I6 engines. The stovebolt era engines had the intake and the exhaust manifold bolted together - with exhaust heat providing the hot spot. When eliminating either of the stock manifolds the provisioning for heat needs to be restored:
in this example bungs on a set of Fenton headers heating a stock intake.
The hot spot ensures proper atomizing of the fuel mixture and prevents fuel from falling out of suspension and pooling in the floor of the intake. This is especially important in temperate climates and more so in winter months - but even in the middle of summer the venturi effect in a carburetor can cause ice-up and cause fuel to puddle in an unheated intake.
