I had a problem with a 440 in a 56 Dodge pickup. After about 20 min of driving the temp would be at 230. Tried reducing the speed of water through the system with no change at all changed the thermostat. No help. When changing the thermostat noticed a couple of inches under it in the housing there was a hole drilled into the other side (inlet). Tapped and put a 1/4 pipe plug in the hole. That cured the problem. The engine would go up to 195 (that was the thermostat) and not go any higher. Can someone tell me why they drill a hole from the inlet to the outlet side of the water pump housing? Anyway, overheating problem solved!