I suspect that you may have experienced fuel percolation as a result of the higher temperature on the return trip. A number of cars in our local MAFCA club have had that problem and I have made a 3/16" insulator for them to bolt between the carb and the manifold using two gaskets and slightly longer bolts. It worked. I bought the material from McMaster-Carr.
WWW.mcmaster.com Gar Williams