Stopped at O'Reilly's and tested the brand new radiator cap and found it weak and leaking down. While stopped we did the hydrocarbon test in the radiator and it was negative, so I don't think we have a engine hardware issue.

Open to other suggestions

That shroud is blocking a significant amount of airflow.  It may not allow enough to cool under load.

If the temps stabilize at 210 and it does not boil over, then it is ok.  210 is not too hot.  It does seem like something is not right but in this circumstance, I would simply keep my eye on it and get it home for troubleshooting.



Lawrenceville, GA

Home is 2500 miles away on the other side of the Rockies!

We went to Lowe's and got some rubber pipe insulation and sealed up the core support to hopefully force more air through at speed. It's fine in town/traffic now.

I could live with 205-210 steady, problem is once it passes 210 it gets into thermal run away, and we have to stop to cool it off.

It does cool off much faster now. Even half way on it's own without water on the radiator. And we can cool it to 145° while idling. Yesterday we could barely get it under 190°

The Studebaker guys found that the brand new  aluminum radiator was beautiful, but the fins on the core were so tightly woven that not enough air could flow through at speed to cool their engines.  Slow speed running was acceptable, but not highway speeds and loads.

John - "The Hoosier Hurricane"

"tested the brand new radiator cap and found it weak and leaking down."

You replaced it and you are using coolant instead of water?

____________________________

Have you verified that the temperature indication is correct?  145 idle is low.



Lawrenceville, GA

Yes new Stant Cap tested at the counter with the same tester used to condem the cap we were using.

It's always had coolant in it. A touch stronger than 50/50 mix

Yes the temp reading is verified correct.

The #304 thermostat is a 160°. We can get to 145° pouring cold water over the radiator with it idling. We only did this once to get it cold enough to safely pull the radiator cap for testing.

From a cold start it will get to about 163° and cycle back to the fan shut off at 155°.

We just checked back into the same motel as last night. Everything we have done has made a dramatic difference. But it still wants to creep at 50mph with any hint of a hill. The good thing is today when it got to 210° we could pull off the road and it will start cooling down on it's own, yesterday it would continue to climb.

We have played with the AFR and timing going down the road and have it set at the coolest settings for our particular combination. We went back to premium gas today and no difference. FWIW ethanol free is 100° hotter in EGT vs E10 of the same octane.

We've decided to wrap the headers and down pipe after we go split a $17.99 Steak and Lobster at the casino.

If that doesn't cure it, we have a igloo cooler that holds 5 gallons of ice water, it'll get a bulkhead fitting, ball valve and tubing to the front of the radiator for corrective cooling while moving.

We also have the old heater box complete with heater core and fan we can plumb/wire and run to help out.

We have the original brass radiator with us, but the top tank has a leak. If we refit that it would take some reengineering of the fan situation as well.

How is your lower radiator hose ? A soft hose maybe collapsing at the higher RPM. More water then coolant is better. I usually use 60-70 % distilled water. Where exactly are you?

I would try removing the shroud.  Most OEM shrouds are contoured to funnel air through the fan or the fan is so large that it is nearly equal in size to the core area, leaving the core largely unobstructed.  And they don't usually have a large intercooler in front of them.  At present, the radiator has a significant obstruction in the front and in the back.

There are "zip tie" style mounting "brackets" you can use to mount the fan directly to the core, https://www.summitracing.com/search/part-type/electric-fan-mounting-brackets-hardware?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=fan+mount  If you have tools, you can make brackets.  A mechanical fan can also be used.  You can remove the fan and shroud on the side of a highway, to test it on an open road.  Neither the fan nor shroud is needed at typical highway speeds.

I've had a thermostat that didn't open completely.  At low speed it cooled fine but above about 50, the temp climbed rapidly.



Lawrenceville, GA