Very nice looking build Tom
congratulations, and I'm looking forward to see what is coming.
Did you make sure to use special silicone sleeves to connect your carbs to the manifold? They look to be the same kind as the hose you use for water to me. If it is so, they will not resist the fuel vapors. You need special silicone hoses, fuel resistant, which have a spacial inside layer (fluorine kind of component if I remember correctly).