I have a 64 C10 that I did an engine swap. Put in a new 350 SB, Champion 4 core radiator, Flex fan with long water pump. 180 deg thermostat.
Here's my issue, The truck takes forever to warm up enough to open the thermostat and during this time it starts puking coolant from the overflow line. When the truck warms up enough to open the therm it heats up past 180 deg to 200.
I replaced the therm thinking it was stuck open but it's still doing the same thing.
Any ideas? Help me before I pull whats left of my hair out.
I'd change the bottom hose to one with a spring in it, and see what happens. The later model Chevys with serpentine belts the water pumps run backwards to the older ones. Just one more thing to think about.