Another Issue with an Edelbrock 1406

[RichardJ]

Ditch the phenolic spacer or replace with an aluminum spacer.

When the air above the throttle passes the nearly closed throttle blade there is a large pressure loss and a temperature loss. When you start it in the morning the throttle blades are held open by the choke high speed idle cam and there is less of a pressure drop.

This sounds stupid even to me, but I think the carb is icing up.

Do a web search for carb icing and you will find most info is about small aircraft engines. An airplane can fly for hours on a warm day with no problems. When they cut the throttle on the landing approach, the carb can ice if they don't add carb heat.