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Background;
1950 239 completely rebuilt by reputable engine shop. Block boiled and magnafluxed. All new internals, heads machined, new pumps etc.
Conditions;
Goodyear Arizona, 106 degrees light wind, fan in front of radiator. No hood or fenders.
Problem;
After initial start with 2 shut downs to fix leaks, I restarted a 3rd time. This time no leaks but after 12 minutes at above idle, the temp gauge pegged at "H". I used an inferred thermometer and the heads were at 220, top of radiator 219 and bottom 213. Water was flowing at the top of the radiator. As the engine cooled we read 1.5 volts on the temp sensors at "half" scale temp which indicated the sensors were working and the gauge was accurate.
After changing the radiator from a recored original to a new reproduction radiator, we restarted the engine.
After about 15 minutes we were pegged at "H" again with similer temps on the thermometer.
I spoke with the guy who built the engine and he wasn't concerned about 220 degrees, as long as water was not boiling out......it wasn't.
Could it be that the engine couldn't cool enough due to the hot air temp?
Why would anyone want "H" to be normal as a temp reading?
Any chance the infrared can be switched between metric and Fahrenheit? 120 is really cool, if Fahrenheit. Way above boiling in metric.
How big a fan? Was it tight against the radiator? Box fans used in houses really don't have a lot of pressure to push thru the fins, but just idling I would think it would be adequate.
Are you sure the engine is full of water, no air bubbles?
Try jumpering the terminals on the temp sensor that has two terminals.
So you have the stock fan, and had a box fan to push air towards the engine? Confused by the "in front of radiator". Do you have a shroud?
What thermostats do you have in it?
Fresh built engines do run hot for a while, but I wouldn't expect it to run that hot, even in AZ this time of year. Can you drive the truck around? Running with no load isn't real good for the rings, as far as seating.
Incorrect timing will make them run hot. Stock distributor and carb?
No shroud, cant find one. Still watching ebay though.
Not really driveable yet, no seat/steering wheel etc.
160 degree thermostats, but I took them out and still have 220 degrees.
Timing checked and is dead on.
Stock distributor and carb.
The guy who built the engine wanted me to run it at "above idle" for 30 minutes, change the filter and then drive it with the break in oil for about 200 miles. I didn't even really get a solid 30 minutes, I got 2 runs of about 18 and he was happy with that. Now I have to retorque the heads.
OK, what the builder wanted was a cam break-in cycle at ~1500? Pretty typical. I would expect it to get pretty darn hot sitting still and at that elevated RPM and no shroud.
After your re-torque are you going to put it together and drive it? BTW the gurus on the Ford Barn recommend torquing to 55, vs the 65-70 the manual recommends. I did that on my last build and it is holding just fine, but I had to re-torque 3x. A real pain with the fenders on.
A shroud will make all the difference in the world. If you can't find one, a sheet metal shop can make one pretty easily, albeit without the scallops at the bottom for the radiator pipes.
If you have clean water passages, a fresh radiator and good water pumps circulating you probably have an air flow problem.
Get a shroud as suggested. Makes a big difference. My stock 239 doesn't overheat and I'm in Tucson. I can't say for sure what the actual temp is though. I just have the stock gauges. Highest it goes is to the middle. I filled rad to just over the tubes and it has never blown out any coolant.
I run less than 50% coolant and have a 7lb cap on a fresh serviced stock 4 row brass rad. Stock 6 blade fan and shroud. Bob Drake pumps. Just walking past my grill, the fan will pull my T-shirt toward the grill at idle. That fan can move some air.
My engine is not a fresh rebuild. It's tired. The T-stats look to be original. Here's a pic of the T-stat and my rad and shroud.
Any good HVAC sheet metal shop can make a basic shroud. It's a classic rectangular to round transition, very common. But you need to tell them what flanges, what width/height, where the round is in relation to the rectangle. And you need the edges of the round beaded to stiffen it.
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