Several years ago I bought a 1954 Chevrolet 4400 with a remanufactured 1958 235. As with the previous owner I struggled with continuous overheating that would not go away. I changed the thermostat and the radiator and then I added electric fans thinking it wasn't getting enough air. It still did not cure the overheating so last weekend I pulled the water pump out thinking it was not circulating. Look at the pictures below and you can see that I found a water passage that is in both the head the block and in the water pump that was plugged solid. Without this passage being open the water cannot flow from the back of the motor to the front of the motor and get the thermostat hot enough to open before boiling. I hope others can use this information and save them some needless expense.
I'm amazed anyone would claim an engine "rebuilt" if they didn't bother hot tanking the bare block to remove all the accumulated rust sediment . I often find 3" or more of silt around the cylinders when I remove the welsh plugs, it's not terribly hard to dig it all out with coat hangers or welding rods... At the very least I'd remove the block drain plug/valve and ensure coolant flows freely out of the hole .
I had the same issue change a bunch of stuff till I touch the water pump, also how did u flush your port out?
I am almost out of the clogged engine block issues this crust is from letting it sit for 3 years with only water in the system
The last two posts show how critical proper periodic cleaning and flushing is . Residual rust will settle in the lower parts of all the water passages and hinder the ability of the coolant to absorb heat as well as create hot spots .
That crust caused my water pump to start leaking engine was heating up on cooler days a leaking freeze plug a leak lower radiator hose glad to say all clear and replaced and repaired all issues including new aluminum radiator with electric fan
