Bill- I have also wondered about the 6 psi pressure and that's why I mentioned it. As for the factory venting on the Rochester carbs, I'll check the shop manual exploded drawing and look for it. My other Rochester carburetors on my other trucks also show signs of percolation flowing back from the bowl into the glass fuel filter after use, but primarily during hot summer weather and not to this severe extent. Probably "summer blend" fuel in use during some of these other trips. This vapor lock condition is usually behind me for the season by late October.

Jerry- The factory thermal insulator is present. I like your idea of bypassing the metal fuel line temporarily as a test. This fuel pump was on the truck when I purchased it 2 years ago and appears fairly new.

Utah York- The manifold heat riser was not working when I bought the truck and I replaced the exhaust manifold with another that I bought on Ebay. I also thought that a stuck heat riser might be overheating the carb. That issue has been fixed now.

The truck idles and runs well with the 6 psi fuel pump when cold. It does not seem to be overwhelming the float needle/seat and overfilling the bowl. These roadside breakdowns on the ride home were a result of fuel starvation rather than flooding. This 57 has been a constant repair project reflecting many decades of neglect by previous owners. I'm still working the bugs out of it so that I can drive it some distance without fear of breakdown. I'm not quite there yet.

Thank you guys!
Dave

1946 Chevy pickup, 1948 Chevy suburban, 1950 Chevy pickup, 1952 GMC pickup, 1957 Chevy pickup, 1939 Chevy pickup