Automotive Stud
Well-known member
How hot did that one get?
How hot can you really run a flathead safely?
- Thread starter Automotive Stud
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Shadetree
Well-known member
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.
Old Henry,
Maybe I am missing something here and I apologize in advance for my ignorance. But the pressure cap is spring loaded, regardless of the outside pressure the spring loaded four pound cap is constant and the less dense air should not affect it. The outside air pressure is less at 10,715 feet than at sea level and if you continue to climb to a higher altitude, the radiator it seems would eventually rupture and the four pound cap would remain closed. Where am I going wrong?
Shadetree
Old Henry,
Maybe I am missing something here and I apologize in advance for my ignorance. But the pressure cap is spring loaded, regardless of the outside pressure the spring loaded four pound cap is constant and the less dense air should not affect it. The outside air pressure is less at 10,715 feet than at sea level and if you continue to climb to a higher altitude, the radiator it seems would eventually rupture and the four pound cap would remain closed. Where am I going wrong?
Shadetree
David J
Well-known member
If you have stock 33-34's waters boiling point is your limiter as they aren't pressurized . Anything up to the drooling -puking point doesn't seem to hurt them . To answer your question in my humble opinion 210 F . Heck my new pickup spends all it's running time at that temp .
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All you have to do is look at your temperature to find out where normal and hot are. New engines are made to run hotter than the old Fords. Pressure and boiling point have nothing to do with old Fords. The pressure should never get over 2 or 3 lbs or the temperature over 210 at the very hottest. G.M.
Old Henry
Well-known member
Don't know if you have ever had any experience with a pressure cooker that your wife might use for canning or other cooking. The purpose of a pressure cooker is to raise the temperature that the water or, in the case of KFC chicken fried in oil in a pressure cooker, oil can get without vaporizing (boiling). A pressure cap on the radiator works the same. But, it is just adding atmospheric pressure to whatever it is naturally at various elevations. So, as I explained before, if water boiled at 212 at 15 psi atmospheric pressure and you add a 4 lb radiator cap it raises the boiling temperature at 15 lbs ambient atmospheric pressure to whatever it is at 19 psi air pressure. If you jumped with that radiator to the moon where there is no atmospheric pressure and all you have is the 4 lb radiator cap then that's all the pressure that's keeping the water in a liquid state and would only keep it a liquid up to 153 deg. Those are two extremes to illustrate how it's not just the radiator cap pressure but the outside atmospheric pressure that combines together to keep the water from boiling at certain temperatures, not just the radiator cap alone which would only keep the water liquid up to 153 deg. without the added pressure of the atmosphere. See the charts I posted in my previous post (#11) to see how it all works together and affects each other - altitude, pressure, and boiling point. The radiator cap is just like the regulator on your wife's presssure cooker or the pressure relief valve on your water heater - to limit the amount of pressure that can build up in the engine to 19 psi at sea level to keep it from exploding. Instead, it will let some water vaporize (boil out) that immediately cools the engine as long as the water is boiling. (i.e. if you keep the engine running after the water's all boiled out it will get hot enough to crack the block as illustrated in previous posts on this thread. But, the engine can never get to that temperature as long as it has water in it.)
As for the radiator rupturing, if you put on a 100 lb radiator cap so that much pressure could build up in the cooling system before opening, I'm pretty sure the hoses would explode or at least the clamps blow off way before the radiator ruptured. At least that's what happened when I tried a 10 lb cap on my Pike's Peak trip. The radiator didn't blow but water started squirting out from under all of the hose clamps. 4 lbs. for the radiator cap isn't something Mr. Ford picked by spinning a wheel, that is the pressure, when added to 15 psi at sea level (19 psi total) that his cooling system is designed to take. Above that, the cap lets the pressure out rather than blowing out other stuff.
P.S. One need never apologize for their ignorance as we all are ignorant to different degrees.
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Old Henry
Well-known member
That's because modern cooling systems use a 15 lb. radiator cap that raises the boiling temperature to 250 deg. at sea level.
Old Henry
Well-known member
Agreed. The big problem with flatheads is not boiling out the water, it's the gas vaporizing in the fuel pump and killing the engine from continuing on or starting. I'm fully confident in Ford's design of the engine and water cooling system and have never had a boil over with all stock equipment. I do think, however, that Ford's location of the fuel pump on top of and at the back of the engine is a poor design that allows vapor lock at way too low of under hood temperatures and have done the same as blucar - added an electric fuel pump back by the gas tank to turn on momentarily when vapor locked to be able to carry on down the road or start if it won't start. Works great every time.
Old Henry
Well-known member
G.M. I don't think you are going to get much support for that kind of bare, bold, assertion that is not supported by any laws of physics. I don't think you believe that either. If you did you'd run all of your engines without any pressure radiator caps and just let 'em boil away.
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David J
Well-known member
Thanks , As long as I made the penalty box here's a better example - the dirt B-mod sometimes comes off track at 260 with the headers glowing a dull orange . Water only of course as per rules . 22# radiator cap . 1,100 ft elevation . Normally not puking unless damaged . Gotta be a tempologist out there that can gimme da dope on dis .
Old Henry
Well-known member
22# radiator cap plus 14 psi at 1100 feet elevation will keep water liquid up to 264 deg. Don't push your luck. Four more degrees and you blow (theoretically, of course).
David J
Well-known member
It only does that on sloppy nights - normal operating temp is 230 . We found that 25# caps sometimes bulge the radiators so 22# is max . The tubes expand slightly & that restricts air flow = junk radiator .The pavement cars run 195 F . They don't collect as much clay in the nose . Anywayz to answer the thread again 210 F is max for a flathead IMHO .
22# radiator cap plus 14 psi at 1100 feet elevation will keep water liquid up to 264 deg. Don't push your luck. Four more degrees and you blow (theoretically, of course).
Blownflatheaddeuce
Senior Member
What Mart said.
185 is a good AVG running temp to get the oil hot enough to work properly, too cold and you increase engine wear, too hot and oil breaks down, rings lose tensions etc....
I run a blown flathead on the street in ALL temps, WITHOUT and engine driven fan. i run a very good rad, decent pumps, ater jacket is super clean, the timing is right and I run straight rain water with a corrosion inhibitor/surfectant. I have an elec fan that i will use in bad traffic on a hot day - but I rarely ever get over 200 and average 175-190.
I think thats perfect in terms of wear, engine longevity, oil life and performance.
BFD
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Henry you read to much and TRY to interpt in your mind what happens or will happen. I believe everything I posted and is supported by my cars which are driven more than most in weather over 85 degrees with temperatures recorded to support my claims. Also developing the turbine impellers for Skips high volume water pumps that are running on several thousand flatheads is SOLID proof that what I post is the best cost effective solution to cool these engines. All fact not fiction.G.M.
Shadetree
Well-known member
Old Henry,
I think I have it. If I would put a partial vacuum over the outside of the pressure cap, the difference in pressure between the inside and the outside of the radiator, 4 pounds in this case, would overcome the spring loaded cap and release the inside pressure permitting the water to boil at a lower temperature.
Thanks, you explained this well.
Shadetree
I think I have it. If I would put a partial vacuum over the outside of the pressure cap, the difference in pressure between the inside and the outside of the radiator, 4 pounds in this case, would overcome the spring loaded cap and release the inside pressure permitting the water to boil at a lower temperature.
Thanks, you explained this well.
Shadetree
fonti
Junior Member
well...not sure about that. My flatheads run between 180-200 in most all the different circumstances. So they're just perfect. Below 180 is not good for the engine, that's what I've been told.
My SBC is getting close to 200 and when I really want to know how fast it goes, then 210 is not unusual...
Old Henry
Well-known member
Ah, now I see that when you said "Pressure and boiling point have nothing to do with old Fords" you meant "Pressure and boiling point have nothing to do with cooling old Fords." The original question was about how hot can the flathead be run safely, not how to cool it. My information about boiling over temperatures and how they are affected by pressure was in response to that original question. Your discussion was on the different topic of how to cool the flathead. So, there's the difference. I agree with you that pressure and boiling temperatures have nothing to do with cooling the flathead, but has everything to do with how hot you can get one before it boils the water out. So, no disagreement, just talking about two different things.
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