Losing Fuel

After the car is parked for several days I have a hard time getting it to start - like no fuel.
After I crank it for a while and pump the snot out of it it will fire and run normal. Somehow it is losing fuel.
I am running an LA340 with Edelbrock 1408 carb with electric choke which is working and a Edelbrock mechanical fuel pump.
All appears normal and it only does it after it sits for several days.
No hot start issues
No run issues
No gas in the oil
No fuel on the ground
No leaks that I can find anywhere in the fuel system
I dont believe it is boiling out of the carb I use a thermal spacer between the car and manifold to prevent this.
Is there any way it can siphon back to the tank?
Im lost