How hot can you really run a flathead safely?

Automotive Stud

Automotive Stud

Well-known member
I have a new Walker radiator and 170* thermostats in my 59ab, it usually runs around 160* but on a hot day in traffic into a car show she'll creep up around 190* It will cool right down once you get moving again. I never thought this was a problem but my dad knows more about these motors than me and he said that's too hot. So how hot is too hot?
 
190* is not too hot for a limited time, all flatheads will get hotter sitting in traffic without air flow through the radiator. If it cools right back to 170*, everything should be working fine. I would suggest (if you haven't already done so) that you have Skip Haney rebuild your water pumps to increase water flow which will drop the engine temperature.
 
If you are using 170 degree thermostats and engine usually runs 160 degrees your thermostats or your temperature gauge is wrong. I don't run thermostats anymore in my 59AB in the summer and have had no overheating issues.
 
I was running 190 degs on gauge 8BA with 180 therms,removed now running along down to 160degs.But when I get stuck in traffic last night it went to 220degs,but when moving along again it took maybe 10 miles to get back down and never went back to 160 degs.I have a new Waker rad,new pumps,timing on,but its .060 over and has 4 sleeves.headers.I think if i could keep it at 200 that high enought.
Think its time for Electric Fan.
 
I'd stop worrying about it. When it's so hot the paint is burning off the engine, that is TOO hot. 190 degrees is nothing.

Mart.
 
Automotive Stud said:
I have a new Walker radiator and 170* thermostats in my 59ab, it usually runs around 160* but on a hot day in traffic into a car show she'll creep up around 190* It will cool right down once you get moving again. I never thought this was a problem but my dad knows more about these motors than me and he said that's too hot. So how hot is too hot?
Click to expand...

Running 190-200* in traffic on a hot day is really not too hot, but 160* on the road is too cold for good engine and oil life, imo, based on factual info. :)
 
I have done all of the `Barn's Recommendations. I have never seen my engine actually boil, but I get nervous while sitting still on a hot day. I finally installed an electric fan and it works. I just use it going through town or slow traffic. When I shut it down and raise the hood with the fan still running I am amazed at the amount of heat blowing from the radiator. Too, I am amazed at the difference in engine temp after a few short minutes of running the fan with the engine shut down. The temp gauge goes to half scale! I know it is a crutch but it makes me feel better.

These engines certainly were not like this when new. There almost has to be some blockage somewhere. I owned Ford flatheads back in the mid `50's. Overheating was never an issue.
 
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At 190 (assuming an accurate gauge) I wouldn't panic, but the hairs on the back of my neck would just begin to tingle. Question is whether it has settled in or is still rising. If it continues to rise until boilover, then you have a problem that needs attention. These cars were designed to idle on a hot day without boiling over.

High temperature at idle is often caused by your ignition timing being too retarded. Just to experiment, advance it a bit and see if it makes a difference.
 
You could also try raising the idle a little bit, to increase fan air pull and water pump flow. Just a little, not revving the nuts off it.

Mart.
 
Maintaining a constant operating temp in the 180/190 range will generally insure clean efficient operation of any engine, especially the flat head Ford.
I can clearly recall the training session on cooling systems when I went through an auto mechanics class in 1950/51... The text of the class, written and photographic, stressed the importance of thermostats, and maintaining an optimum temp of 180 degrees.
We all know that water boils at 212, however only a fool runs water in a cooling system.. A 50/50 mixture of coolant/water will not boil until about 230/240, a pressure cap will increase the boiling point 3 degrees per pound.. A modern system with 50/50 coolant and a 15# cap will not boil until the temp gets over 270/280 degrees.
A low pressure cap in the 5/6# range with a coolant recovery tank works very well on the older style of radiators.
Head gaskets blow and blocks crack as a result of steam pockets in the cooling system caused by a system that is low on coolant and/or has been shut down because the system was boiling and cool water was pored into the radiator.
I have operated my '36 Ford in the blazing deserts of Nevada, daily traffic in Vegas and Southern California with the temp gauge sitting at about the 3/4 mark. The engine never boiled. On the occasions when it wanted to vapor lock I turned on the electric fuel pump and kept driving.
 
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If it ain't boiling over, it ain't too hot.

Here's a clue. The 59AB has one temperature sender that sends variable signals to the gauge depending on the temperature and another that is a "circuit breaker" that opens and sends the gauge to maximum at a temperature that Ford thought might be approaching boiling over. At that point, the gauge will read the same as when the key is off. That's a point to possibly get a little nervous. But, even then, if it ain't boiling over, it ain't hurtin' nuttin'.

Need even more detail? Here it is from a previous post of mine:

Too hot is the temperature that the water boils out of the cooling system. Any temperature up to that point doesn't hurt the engine.

At sea level without a pressure cap on the radiator that temperature is 212 deg. With a 4 lb. stock radiator cap, that raises the boiling temperature to 225 deg. So, anything above that would likely be "too hot" for a flathead at sea level, meaning that the water presssure would likely overcome the radiator cap pressure and boil out.

That boiling temperature decreases with altitude. So, at the elevation that I live at, 4,800 feet, the air pressure is only 12 psi. Adding my 4 lb. radiator cap, my water should boil out at 219 deg.

At the highest paved road in my state (Utah) - Bald Mountain pass - 10,715 feet, the air pressure is 10 psi. Adding my 4 lb. cap lets my water boil out at 210 deg.

At the top of Pike's Peak, 14,114 feet, the air presssure is only 8 psi. Adding the 4 lb. radiator cap will only keep the water in the radiator up to 202 degrees.

So, at the elevations that most of us live at we should consider too hot for a flathead to be above 220-225 deg. That being the case, I think we all have a much greater margin than what we think we do between what we think is too hot and what is really too hot. My temperature gauge is only 210 deg in the middle of the hot mark - still 10 deg. to spare at my elevation, 15 deg. at sea level. So, when the gauge looks too hot, I'm really not; unless, of course, I'm on the top of Pike's Peak or maybe even Bald Mountain Pass. But, those elevations usually include pretty cool air so overheating usually isn't a problem.

My calculations made from data on this chart: http://www.engineeringtoolbox.com/bo...ter-d_926.html

And this one: http://www.engineeringtoolbox.com/ai...ure-d_462.html
 
You'll find that the engine runs smoother and cleaner at 180* to 200*. Needs this temperature to get the moisture out of engine and stop from forming sludge. If you running ambient temperature plus 100* your safe.
Butch
 
The stockcar ran 210-220 most of the time. Ran a MOPAR 4 core radiator with 7 lb cap. Most cars ran about the same, some even hotter. So I don't think 200 9s too much and won't do any harm
 
Question; what is a hot day? Is the Walked radiator the same thickness, meaning the same amount of rows? Do you have a fan shroud? There is nothing wrong with running 100% water, it's a far better coolant if you add the proper rust preservatives. If you vehicle is able to maintain normally 160, then you have a air flow problem. You need to check further in to your problem.
 
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Thanks for all the responses! I agree I've noticed it runs better around 180* but the challenge is getting it to run at that temp all the time. I tried running without thermostats and it took forever to warm up and ran around the same temperature. I also like to use the car in the spring and fall so having thermostats is a must.

The walker is the same size as the original, I run 50/50 water and antifreeze as I don't have the car in a heated garage in the winter. Stock 4 blade fan and no shroud except for the factory tin pieces.

So now the question is how can I get it to run warmer in cooler weather?
 
To run a constant temperature you need a constant air flow and a constant temperature coming out of the engine. And a slow acting temp guage. Won't happen!
 
190 to 200 driving down the highway is to hot. This leaves you no safty margine in traffic on a hot day. A hot day is over 90. When moving above 25 miles an hour you have the forced air from the forward motion of the car cooling the radiator. There is a differance when heading into the wind which cools better even though it takes more engine power than with a tail wind. I find unlike some others that faster speeds don't mean higher temperatures. I drive at 65 to 70 plus and on a two day 1,200 mile drive 2 years ago with temperatures over 100 both days it ran at 175 to 180 at highway speeds. I didn't have any overheating in towns but had problems with the new gas a few times. When I say over heating it never got over 200 in towns. Everything on my 39 convertible is stock except a working pressure cap and Skips pumps. Modern stats don't work in these engines when it gets over 85 outside temp. The flow opening is to small and causes overheating from less water through the radiator when it's hot out. Skips pumps provide almost double the water through the radiator and entire system. I have installed Bob Shewmans 180 degree stats in my 39 conv.and 39 P/U and have been running them for over 4 months and both engines are right at 178 to 181 every time I check them. The hoses have a 1 3/4" ID and the stats heve at least a 1 5/8" ID opening so no noticeable loss of flow is indicated as far as temperature rise. Bob's stats sit in the hoses and are held in place by the radiator output necks and can't move. Bob can be contacted at 1-610-933-6637 or gadgiteer@aol.com I also find the engines run nice and smooth at 180 and get up to 180 in about 5 miles. After the stats fully open at 180 they stay wide open and act like they are not there, the same amount of water flowing through the system as if it didn'thave stats. If the temperature drops below 175 the stats will partialy close until the water gets to 180 and open again. This would be a continious cycle at say 50 degrees out to keep the engine at 180. The real problem with stop and go or slow driving in hot weather is the design and on some years the location of the fan. The stock 4 bladed fans provide a boarder line amount of air, the crankshaft mounted fans move air against the front engine like hitting a stone wall. G.M.
 
Automotive Stud said:
I tried running without thermostats and it took forever to warm up and ran around the same temperature. I also like to use the car in the spring and fall so having thermostats is a must.

So now the question is how can I get it to run warmer in cooler weather?
Click to expand...

I think you answered your own question. Do like Mr. Ford said. Leave thermostats installed all year round. Stock ones work fine. Leaving them out is no cooler in the summer (I've tried it both ways and it made no difference). And leaving them out causes the engine to run too cool in cool weather and not warm up to operating temperature fast enough in hot weather.
 
blucar said:
Maintaining a constant operating temp in the 180/190 range will generally insure clean efficient operation of any engine, especially the flat head Ford.
I can clearly recall the training session on cooling systems when I went through an auto mechanics class in 1950/51... The text of the class, written and photographic, stressed the importance of thermostats, and maintaining an optimum temp of 180 degrees.
We all know that water boils at 212, however only a fool runs water in a cooling system.. A 50/50 mixture of coolant/water will not boil until about 230/240, a pressure cap will increase the boiling point 3 degrees per pound.. A modern system with 50/50 coolant and a 15# cap will not boil until the temp gets over 270/280 degrees.
A low pressure cap in the 5/6# range with a coolant recovery tank works very well on the older style of radiators.
Head gaskets blow and blocks crack as a result of steam pockets in the cooling system caused by a system that is low on coolant and/or has been shut down because the system was boiling and cool water was pored into the radiator.
I have operated my '36 Ford in the blazing deserts of Nevada, daily traffic in Vegas and Southern California with the temp gauge sitting at about the 3/4 mark. The engine never boiled. On the occasions when it wanted to vapor lock I turned on the electric fuel pump and kept driving.
Click to expand...
Whoops, looks like I've been called a fool. I run water in my cooling system in the summer.
 
Too hot and this is what happens
Lawrie
 

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