Driving home in 90 degree heat with a 49 convertible, stock 8ba, skips pumps and factory thermostats with larger opening my car was routinely running on the H but not boiling over. I could cool it down running below 60 mph. Running 70 on the downhills did not help but coasting the downhills and then engaging the clutch would cool it down. In other words blowing a lot of air through the radiator with the engine at idle would cool the water. The gauge did not drop until I raised engine rpms and circulated the coolant into the motor. This actually make me think water flowing too fast through the radiator is a real thing.
Memorial Day I did a mile and a half parade and it got to the H but as soon as I pulled away the temp came down. I am not sure if this is due to lack of flow at low rpms or lack of air flow. I would need to check temps in different places to figure that out.
Running at 55-60 in all temps usually has it about 3/4 of the way so I am eliminating any blockage issues. It is obvious the radiator can cool properly. It is a recore when I restored the car about 12 years ago. In the end I can live with it like this but appreciate any ides and thought some of you might appreciate my observations.
One other thing. On my cross country trip I did not experience any issues but temps were a bit cooler and I was running a chevy dist for the modern advanced mechanism. I went back to stock as I installed a pertronix. Cause condensers suck. Just adding that because I know bad timing can make an engine run hot. It can make a woman run hot too but that's fro another thread.
