47-55.1 Continued overheating issue

[TX3100Guy]

As some of you may recall, after three years of restoration on my 1953 Chevy pickup, I encountered some major overheating issues. For a reminder to folks who followed my adventure and for the folks who are reading this for the first time, let me give you a brief background on the truck and the issue,

The Truck
It is a 1953 five-window with a 1959 261 cubic inch straight six engine. It also has a 1957 McCulloch supercharger from a 1957 Studebaker Golden Hawk and a Vertex magneto.

Due to the mounting location of the supercharger, I had to have a custom aluminum radiator constructed to move the lower outlet from the passenger side to the driver side. As a result, the lower rad hose goes from the lower drivers side, under the oil pan and up the side of the block to the water pump inlet. Also given the squeeze of the engine in the engine compartment, there is literally no room for a mechanical fan attached to the water pump. I have electric pusher fans on the front side of the radiator.

The Issue
I cannot drive the truck more than a few miles before I see the water temp gauge creeping up to 200 degree and higher. I have to pull over, open the hood and let the engine cool down for 20-30 minutes to drive home or to the destination.

My first attempt included removing the one 3,000 CFM electric fan and replacing it with three 2,000 CFM fans. I also swapped out the thermostat from 180 to 160 degrees. I replaced the lower rad hose with one with an internal steel spring to avoid it collapsing and restricting water flow. I also lowered the temp setting on when the electric fans would kick in to 150 degree. Lastly, I installed an air damn under the radiator to create a low pressure when driving to help get hot air out from the engine compartment.

I also installed a digital temp gauge to ensure I was reading the gauge on the electronic instrument panel, since it is only marked 120 - 200 - 280. I wanted a more accurate reading of the temp.

The Result
In short, no change. I can drive a few miles further than before, but once I stop at a traffic light the temp gets to over 200 degrees and will continue to climb if I didn't pull over.

Today, I ran the engine at idle in the shop and used my temp gun to calibrate the electronic gauge progress. At idle (about 1,000 RPM) the engine got to over 200 in about 10-15 minutes. At 210, I shut the engine off, let the electric fans continue to run, and put my large shop fan in front of the truck to cool things down.

On the advice of a friend, I let the engine get up to over 160 with the radiator cap off to watch to see if I could tell that the thermostat opened and water movement started. At 160 'ish I did see the movement of water, not terribly fast, but it clearly was moving. His next suggestion, was to pull the thermostat and see if removing the restriction resulted in any cooler operation. Since I'd have to remove some coolant to do that, I decided to try all of this first.


I am at a total loss on how to proceed or what to try next to resolve this major issue.

Could it be the thermostat?
It is a new water pump? The belt is not slipping and its turning properly.

Thoughts.