Why

[30-9]

Why would my 39 on very hot day in local traffic run at 185 and if I go on high way 60-65, same very hot day, for 3-5 miles the temp go up to 195-200

[JSeery]

Your putting more energy (heat) into the system and it is overpowering the cooling capability. You might have more air coming through the radiator but it is not enough to overcome the increased heat load. The most likely culprit would be the radiator, but missing original shields can be involved.

[30-9]

Thanks JS

Is it safe to assume, for a long run on highway 200 is ok for car or should I limit long drives.

[JSeery]

It's not a problem until it boils over. Heat isn't to much of a problem, but boiling is. Bubbles start forming around the cylinder walls and act as an insulator and drives the heat up even more. Sorta like a runaway situation and it is not good on the engine. So, as long as it's not boiling it should be fine. How are you determining the temp level? Heat gun, separate high quality temperature gauge?

[30-9]

No boiling and car runs great.

Analog gauge on one side stock red on other - both seem to be reading just about same temp.

Thanks again

[JSeery]

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Might be worth getting an IR heat gun to check the temps. They are fairly cheap!

[Ford Freak]

Originally Posted by JSeery

Might be worth getting an IR heat gun to check the temps. They are fairly cheap!

Yep , X2 !!

[flatjack9]

200 is no problem if it doesn't burp coolant out. The warmer an engine runs, the more efficient it is.

[rockfla]

Originally Posted by JSeery

Your putting more energy (heat) into the system and it is overpowering the cooling capability. You might have more air coming through the radiator but it is not enough to overcome the increased heat load. The most likely culprit would be the radiator, but missing original shields can be involved.

JSeery
Couldn't the speed in which the coolant is flowing through the system ALSO possibly be an issue....I know "some" who have run NO thermostats experience this AND or "higher flow" water pumps????

[JSeery]

Originally Posted by rockfla

JSeery
Couldn't the speed in which the coolant is flowing through the system ALSO possibly be an issue....I know "some" who have run NO thermostats experience this AND or "higher flow" water pumps????

That is one of those topics like what oil to use. IMO the original system with the original flow rates works fine. But others love the high flow pumps and believe they improve the cooling. To me it is more of an issue of a clean block and a radiator that is the proper size and functioning properly. These engines were designed to run with thermostats in place. They get the engine up to operating temperature quicker and establish a minimum operating temp. Above the minimum depends on the cooling system function properly.

[Ziggster]

As mentioned, at highway speeds engine is doing much more work which equates into more rejected heat. Despite increased airflow and coolant flow, coolant temps rise means heat exchanger (radiator) cannot reject the added heat fast enough (would require more surface area on radiator) to maintain previous coolant temp. Also keep in mind that coolant temps typically rise 1 degree for each 1 degree increase in air inlet temp, all else being equal. So yes, on hotter days expect to see a proportional increase in coolant temps.

[tubman]

I agree with "JSeery". No thermostats and "high flow pumps" (at least in later flatheads) are a band-aid for other cooling system problems. Solve the problem; don't treat the symptoms. I was "keeping up with traffic" at 80 on the interstate last week, and my temperature went to 190, rather than the usual 170 I see all the time. I didn't think it was unusual at all.

Bottom line is that the Ford engineers really did know what they were doing "back in the day".

[drolston]

Just been through an epic battle with overheating on my big inch flathead. Removing thermostats and going from .045 to .047 jets both helped cooling at interstate speeds (60 - 70) little bit (about 10 degrees total), but what solved the problem was going from that little Champion aluminum radiator to an original Ford truck radiator which has about 50% more cooling area.

[30-9]

Thanks Guys. I agree with most of the feedback. But st top of list, I agree hotter with out boiling the better. Highway 190 or even 195 is good.

Cars 80 and I’m 84. It has a lot more drive than I did at 80.