They other day I drove a bit. It was about 93 degrees
I also installed the higher flow mopar water pump.
The stat controls the
MINIMUM coolant temp.... unless it is defective.
The system efficiency controls the
MAXIMUM coolant temp.
Maximum efficiency usually occurs between 30 and 45 mph.
If you are having troubles above say 35 mph, then you have a system problem; usually a too small rad, or not enough air flow thru it or a coolant circulation problem,; unless the stat is stuck.
If you are having troubles below 30 mph, this is usually a fan/shroud/circulation problem.... unless the stat is stuck.
To prove the stat is Ok you can remove it; but then you have to install a flow-restrictor, to simulate the flow that the stat was supposed to provide. You can buy a restrictor, or you can make your own by just gutting an old stat.
They say, and I have no way to argue it, that if you completely remove the stat, it will upset the circulation pattern designed into the system, by Ma-Mopar. The end result they say, could be localized hot spots in spite of what the temp gauge says. Since those guys were way smarter than me, I don't question that stuff.
Your pump should have had an anti-cavitation plate attached to the vanes.
Your lower rad hose should have an anti-collapse spring inside it.
Most of us severely restrict the bypass hose, forcing most of the water to dead-head at the stat. I left about a pinky-sized hole for bypassing when the engine is cold, and I use the heater core for a bypass off season (blocked in summer) and for emergency; which I have never had to use.
On your combo, You might want to consider your cruise-timing, which I imagine should be between 42 and 56 degrees depending on the actual cruise rpm. Retarded idle and cruise timing produces heat, most of which goes into the exhaust, but it has to go thru the exhaust ports to get there.... while it is still burning. And, since the piston is rapidly falling, exposing more and more cylinder to the hot expanding gasses, the heat short-cuts into the water jacket. What I'm saying is your engine needs a working vacuum-advance system.
And your carb should be getting fresh cold air.
An IR gun is highly recommended. Find the hottest spot just below the stat, and mark it. Then compare all future testing at that spot.
Idling with the hood closed is a good test to see what is going on. If you can stabilize the idle temp, then you are well on your way to solving heat issues.
