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Flathead RUNS HOT - won't cool.

Discussion in 'The Hokey Ass Message Board' started by ace high, Apr 17, 2012.

  1. ace high
    Joined: Dec 15, 2007
    Posts: 202

    ace high

    I too feel that a quality copper radiator would transfer and disipate heat faster than aluminum. But not sure I agree with flowing water a fast as possible. The water has to be in the radiator long enough for the "air flow" (fan) to aid in transfer of heat.
  2. ace high
    Joined: Dec 15, 2007
    Posts: 202

    ace high

    Have done a cooling system pressure test with no leakdown. Overflow with the 7# cap comes about when water gets so hot that it expands enough to overflow. NO Steam out thou.
  3. I just read your first post again. The radiator tubes are too big. Set a coffee can of hot water and soup can of hot water at the same temperature on a surface. Which one will cool quicker? It takes a longer time to cool a large amount of water than a small amount of water.

    It is a nice looking car. I bought a Brass Works radiator for my Model "A" and I can run without a fan. I do not have a hood. I like direct read temperature gauges. I had a nozzle placed on top of the radiator for a mechanical temperature gauge and I can read it from the drivers seat. I think it is about 3" in diameter.
    Last edited: Apr 17, 2012
  4. ace high
    Joined: Dec 15, 2007
    Posts: 202

    ace high

    Ya- I always felt that more small tubes were better than fewer large tubes. More surface area to be in contact with water and air flow.
  5. Voodoo Trucker
    Joined: Mar 25, 2009
    Posts: 44

    Voodoo Trucker

    Hi Ace, you're on to something with the radiator. Best way to check it is to use your temp gun and measure the difference between the top and bottom ports. Obviously there should be a delta there of 10-30 deg, the higher the better..right.
    One, brass is a better conductor than aluminum, use less glycol and use a wetting agent like Redline or 40-Below and use distilled water as the the minerals in normal water can act as barrier to transferring heat. Second, with the cap off check the flow in the neck as the engine warms up and the t-stats begin to flow, is it just flowing too fast or not at all? The large tubes sounds like it may be flowing to fast through the radiator to move any heat off. I ran a 3 row 5/8 in my 46' with a slightly warmed over engine and it never got over 200 in the AZ heat.
    So, check your delta then check the flow, once you get it figured out you'll be able to run a 7lb cap again. Best, Steve.
  6. flatjack
    Joined: Feb 13, 2007
    Posts: 893


    The faster the water flows, the better it will cool. PERIOD. Heat loss (or gain) = flow rate x fluid density x area x temp difference. Increasing the flow rate increases heat transfer. You can't fool with Mother Nature.
  7. George/Maine
    Joined: Jan 6, 2011
    Posts: 949


    I,m not over heating but my new gauge say 210 iding and running along stays at 190 degs with 180 tempstats,New Walker Radtior,new pumps.I have EAC mercury heads and 255 with .060 over.This engine running good now with new Raditor,but runs hot.
    The only thing I can think of and I know its sleeved on one side. boring them out doesn,t make them run cooler.I,m reading with new SW gauges on Pass side.
  8. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,950


    your not thinking your way thru the whole of the situation.

    On one hand you need the water to spend a certain amount of time in the block to absorb excess heat while at the same time you need the water to run thru the rad to shed excess heat.

    Using your statement, you would indicate that the faster you circulate the water the more it will dissipate heat but at the same time it will pick up less heat inside the engine.

    There is a fine line between moving water too quickly and moving water too slowly.

    -The faster the water flows thru the block the less heat it absorbs
  9. trollst
    Joined: Jan 27, 2012
    Posts: 1,757


    Wow, some good ideas, I'm not with the faster water flow crowd, the longer the coolant stays in the rad, the more it'll cool. When the thermostat first opens, you'll see the temp guage drop off, the thermostat will close and reheat the coolant. Its just like that, thats what thermostats are for. I have a 36 ford pickup that will idle all day long, stock g.m. electric fan, 195 thermostat, 4 lb cap. Any day, any ambient temp.
    Aluminum rads cool better than brass rads, its fact, the longer the coolant gets to stay away from the engine, the more heat it will transfer to the open air, a rad is nothing more than a heat exchanger. Are you sure your guage is accurate? An infrared gun is your friend, borrow or buy one, check thermostat outlets, exhaust port temps, find out where the heat is coming from, are both banks pushing the same coolant temp numbers? Are all the exhaust ports the same temps? They should be within a few degrees, I'd look at a richer mixture, lean motors run hot, I'm betting its not complicated, you'll find it.
  10. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    from Central Ca

    Yes Doug, my block produced about a half a coffee can of casting sand from when Henry cast it way back when.
  11. The longer the coolant stays in the engine the warmer it will get. Take a piece of steel pipe that is out in the sun. A 4 inch by 8-10 feet long. Connect one end to a garden hose and the place a valve on the other end. Open the valve on the discharge end a fourth. Measure the temperature of the of the pipe after three minutes. Then let the pipe get warm again, then open the discharge valve all of way. Measure the temperature after three minutes. Which one would have the lower temperature reading.

    Please provide me the "R" values of cooper and aluminum and then tell me which one cools better. As long as you are looking up the "R" value provide yield strength of cooper and aluminum. I think cooper will have a lower "R" value and a higher yield strength.

    A higher pressure radiator cap will not make the engine run cooler. The higher pressure cap will raise the boiling temperature of the coolant. Instead of boiling over at 212f it will boil over at 230f or something like that.
    Last edited: Apr 18, 2012
  12. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,950


    First things first,
    You haven't told how fast you are turning your engine when it begins to run hot.

    Consider this;
    Flatheads are not 6000 redline/rpm small blocks.
    -We are used to our newer small blocks revving easily and effortlessly and seldom do we jump in the Flathead powered hotrod and consider it's original purpose.

    Flatheads are not meant to be spun at a higher rpm for extended times.
    When our Flatheads were designed and built there was very little actual paved roads in the country and the national speed limit was 45 on the best highways but more often than not the limit was 35 or 40 on the good roads of the day.

    The Flathead was designed around running and revving in and around 2500 rpm all day.
    The farther you deviate above that rpm range the hotter it will run.
    This is because the coolant has little time to absorb heat inside the engine and therefor cannot dissipate the heat during the short time the fluid is in the rad.

    Slow the fact down, Find a suitable highway that will allow you to go for a more leisurely 'test' drive. Keep your rpm's in the 2400 to 2600 rpm range and watch your temp gauge. Maintain this speed for 1/2 hour.
    Now speed up several hundred rpms and watch the temp gauge gain a few degrees.
    Speed up by a few more hundred rpm and watch that temp gauge approach hot.

    It is important to consider that once you get an engine hot it is much harder to bring it back down.
    Certain systems will loose water through steaming it away. In earnest, an engine starts to really steam at about 180 degrees and at that time the steam may begin to escape the enclosed system. The more you run your engine into the higher temps, the greater the chance of your system loosing valuable cooling fluid.

    What are you running for coolant?
    Water is a far superior heat exchanger than anti freeze. Antifreeze actually retains heat and that's defiantly not what you or I want in a hot running engine.
    Do you need to run 50/50 antifreeze? Probably not unless you are driving the roadster year round.
    I ran 10 or 15% Prestone antifreeze in my '41 (without thermostats) and it ran nice and cool at 170.
    The small amount of Prestone was used for it's anti rust inhibitors and that's all. I am always careful to drain everyone of my vehicles in the fall as none are driven thru winter.


    Lets get technical:

    Nucleate Boiling and Self Perpetuation...

    There is a certain rate of flow between zero and infinity that the radiator and impellers will do their respective jobs.
    This is true to the laws of thermodynamics....

    Stop the rate of flow and it over heats.
    Exceed that rate of flow and it over heats.

    Regulate the system -as a whole- to within the system's designed parameters and you get peak efficiency of the system in it's enclosed environment.

    Consider this...

    Water/glycol retains heat.
    Air flow dissipates heat.
    That's basic thermo dynamics.

    First, It's important that we don't confuse the -rate of heat absorption- of a fluid (inside the engine) with the rate of heat dissipation- thru the air movement at the rad (copper fins).
    Although related, they both absorb and/or dissipate at different rates as water is more or less an insulator and air (movement) is the opposite in that it quickly dissipates heat.
    ....And Air movement thru the copper fins of the rad is far more efficient at dissipating the heat then is the ability of the fluid in absorbing it (inside the engine).

    So if we take away the ability of the rad to dissipate heat, the system will self perpetuate...

    Consider that at a given rpm, the water pump(s) start to cavitate which creates air bubbles and pockets of steam. (There is a fine line between too much flow and too little)

    Now this is where your engine rpm and highway driving speed come into play,
    When you start to spin the water pumps too fast, the air bubbles caused by the cavitation of the fins of the water pumps (over speed) start to create air pockets that set up the perfect conditions which promote Nucleate Boiling.

    The effects of Nucleate Boiling:
    Nucleate Boiling, or the air bubbles and pockets set up by over-speeding (and cavitating) the water pumps create a insulator of their own in that;

    A: Little or no heat (from the metal surfaces) is transferred to the liquid which could then be transferred to the rad/fins for cooling (in essence, there is an air pocket/bubbles sitting in-between the hot metal surface thus blocking coolant/liquid from dissipating that heat).

    B: allows the metal surface of the head and/or block to become many times hotter than the liquid that is held in suspension millimeters away from the metal surface by Nucleate Boiling.


    Consider This,
    Many people are not aware of the true temperature of the surrounding micro sphere that is Nucleate Boiling.

    ....Your exhaust temperatures are about 1150 degrees while on the water jacket side of the cylinder wall, the actual combustion chamber is around ~600 degrees.
    To maintain that ~600 degrees, the system depends heavily upon the surrounding liquids and their designed heat absorption/rate. While the heat of the cylinder wall (in the water jacket) may be 600 degrees, the movement of the coolant helps to keep it from sky rocketing any higher where it will start to self perpetuate..

    Now if we were to take away the fluid contact (absorption) via a steam pocket (caused by over revving/cavitating the water pumps), you effectively raise the temperature inside the water jacket/head to at least the 600 degrees of the adjacent cylinder wall and that in itself is a game changer....

    Along comes Nucleate Boiling.
    Nucleate Boiling can irritate the temperature of the cast metal to extreme temperatures that cause the cast (cylinder walls) to blister both inside and outside the combustion chamber.

    These extreme temperatures are blocked from being absorbed by the fluid in the water jacket due to the air bubbles and pockets that were set up by cavitating the system.

    The temperature of the cooling system becomes self perpetuating once you start to cavitate and begin to overheat the system.

    You yourself have seen Nucleate Boiling thousands of times in your life...
    ...Every time you put a pot of water on the stove you have witnessed this.
    The element of the stove exceeds 1000 degrees (just like your combustion chamber/heat of combustion)
    As you look at the boiling water you notice tiny bubbles at the heat source (just like the inside of your water jacket). The bubbles expand as the move from the hot steel/bottom of the pot up to the surface.
    It is those bubbles cause tiny blister in the machined surface inside your cylinder walls as well as they effectively block water from cooling the surface of the metal.
    Now while the water and steam coming off the boiling pot of water is 212 degrees, the temperature at the metal wall is much higher while the temperature off the element is higher still.

    Self Perpetuation happens when you have cavitated the system by over speeding the water pumps thus creating air bubbles that get trapped in nooks and crannies which in turn begin to block the water from touching and absorbing heat from the metals surface. As the temperature rises, Nucleate Boiling kicks in and creates its own air bubbles further impeding the ability or the water from drawing (touching) heat from the cylinder walls inside the water jacket.

    The best thing you can do to keep the system in check is ->Don't Cavitate/Over-speed The Water Pumps<-
    Or ->slow the fact down, change your rear ratio, ad an overdrive and remember that a Flathead is designed to continually operate at and around ~2500 rpm.
    -The Flathead is/was a design that suited the 45 mph speed limit of it's day and rear ratios reflected a 2000 to 2500 rpm range at highway speed in 1950.

    All Just My Humble Opinion,


    ...There is lots of information available regarding Thermodynamics and/or physics on the net.

    For those that do not understand or believe in Nucleate Boiling, do a Google search in regard to the basic laws of thermodynamics and heat dissipation then post your comments here..
    Last edited: Apr 18, 2012
  13. deto
    Joined: Jun 26, 2010
    Posts: 2,621


    I don't have a fatty but I fixed an over heating issue by pulling the thermostats and tacking a washer in the thermostat housing so that the water flow is regulated enough to spend enough time in the radiator and be cooled
  14. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,950


    And where is the air movement/Radiator in your equation,
    There isn't any, you are missing half of the equation.

    It's important that we don't confuse the absortion rate of a liquid (inside the water jacket)
    with air movement and it's ability to dissipate heat (radiator), they are 2 different equations.

    Each and every heat exchange system, whether it's an air conditioner or a Flathead engine needs both absorption and dissipation to operate correctly.
    -An air conditioner cannot operate without it's condenser and a Flathead cannot operate correctly without regulated and controlled absorption and dissipation via radiator/air movement

    There is a fine line between too fast a fluid flow and too slow. The system is designed to pump so many gallons per minute for peak efficiency. Exceed it, you overheat, pump too slowly, you overheat..

    Furthermore, If you placed an incorrectly sized/small radiator in the system then no matter how long/short the fluid stays in the engine it would not get enough of the cooling side of the equation.

    Last edited: Apr 26, 2012
  15. WOW !! now thats a good HAMB tech thread ,lots of info.
  16. George/Maine
    Joined: Jan 6, 2011
    Posts: 949


    Does that engine have a road draft like a 8ba whats the little hose,another thing your belt maybe slipping due to the angle not using your fan pulley.Have you ever used a regularl fan,even with just the pulley no fan at driving speed and see if temp drops.
  17. ace high
    Joined: Dec 15, 2007
    Posts: 202

    ace high

    Draft tube removed and PCV installed. Belt angles are similar to stock. Fan pulley would have been on a separate belt and pulley.
  18. ace high
    Joined: Dec 15, 2007
    Posts: 202

    ace high

    Hey Moe Thanks for the detailed info. In my case engine speed seems to be a mute point. I'm getting the same results whether at idle, In town cruising, or highway. R/E ratio is under 3:1. With my driving engine rarely sees over 2500 RPM.
    I'm leaning toward a heat disipation issue-- Insuficient Radiator ???
  19. Smokey2
    Joined: Jan 11, 2011
    Posts: 920


    Repeat ! Run Temp gauge on both's even Fun, to watch Thermostats
    Open at Different Times .
    Leave Therms IN, Yes IN ! One thing Inher-ant of Flatties Was, Coolant went thur Radiator TOOO Fast, did'nt have Time To Properly cool it, One Trick.....Cut every Other Impeller OFF WATER PUMPS. 'Nuther Trick, Place Large (heavy) Flat Washers inside Water Hoses (Inside ! , Hold In Place with Std. Clamp, outside....!
    (dummie !)...................
    Ran several Flat 8's Ferds , Mercs, V-12 Lincolns..........One Buick ('48 Conv."....
    when went on Drives with buddies In Early Ford V-8 Club, Had to put card board partially covering Radiator to git engine Warm Enought !
    On reast Stops, I (always !), helped carry Water Fer Tha' Ferds !!!!!!
    Yeah, Got Chevies Now , can't keep'em running properly !!!!!!

    Smoke 'em If U Got'em........Ain't got one ?
    Bum off Your Buddie ! an, Have Fun Day . Little Johnny, still plays
    with "Hot Wheels ".
  20. I agree with that, especially with the larger tubes and subsequent loss of surface area which greatly aids heat transfer that you need.

  21. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    from ma

    I haven't read every reply to this thread, but I've read most everything the OP has posted.

    Aces, keep your 6-7lb cap. since you don't have a recovery tank like a modern cooling system you have to let the water push out until it finds its own level.

    I'm not a fan of those big tube aluminum radiators, never tried one, just felt it would be a waste. I'm currently saving for a walker as the top tank in my stock 32 radiator is thinning out and making pin holes :mad:

    my other question is, why are you running poorly at 210?? you should be able to run there without any problems??
  22. I missed this before. Aluminum heads transfer heat from the combustion chamber to the coolant a lot better than cast iron heads. Cast iron is a great heat sink, it doesn't want to give it up. Like the cast iron radiators in old houses.

    At the same time the inherent properties of the aluminum also give off heat on the external surfaces, that's why so many are finned, to take the surface area advantage. All in all, they are a improvement over cast iron heads for cooling.

  23. revkev6
    Joined: Jun 13, 2006
    Posts: 3,351

    from ma

    Aces, i just looked again at your motor and see that you are running a late block with early heads. what distributor are you running?? if that is a new mallory, supposedly they have the wrong advance curve for a flathead. I forget the actual curve (ask gmc bubba for a real answer) but I think it's supposed to be all in by about 1,000 rpm while the mallory unit runs a sbc curve which comes in much later. might be an issue for you.
  24. AV88
    Joined: Feb 7, 2011
    Posts: 235


    It could also be somthing as simple as your thermostats not opening or put in upside down or your fan may be faulty and not working 100 percent of the time you think it is ,its happened to me, good luck I hope you figure it out and enjoy that neat car
  25. Terrible Tom
    Joined: Feb 15, 2010
    Posts: 573

    Terrible Tom

    Possible cracks in the block around the valve seats? Common problem with flatheads.
  26. flatjack
    Joined: Feb 13, 2007
    Posts: 893


    No, the equation clearly shows that with faster flow, more heat will be absorbed in the engine.
  27. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    TIMING! Sounds like everyone is just using the word, presumably referring to setting the idle timing.
    The potential issue is the ADVANCE as you run. If it is not advancing adequately at your running speed it will rapidly build heat, even faster than a retarde modern motor because all the waste heat is going through the water passages on its way out.
    What distributor?? If stock 8BA, it is very likely you have little or no actual advance. You CANNOT check the curve on these things by revving in your driveway, and setting them up on a machine is potentially VERY deceptive because the pressure drop used on the machine is unlikely to match that seen in use.
    If Mallory of the recent sort, these seem to be shipped with random curves, some set so tight they don't advance significantly at speeds of normal use.
    If you find or suspect advance problem, you can make a crude check by temporarily bumping the static timing up with engine already running. Obviously, stop the experiment if you hear pinging...
    A good flathead will run all day at any RPM it can reach without rise in temp. I collected many an 80 MPH ticket in my '48 on long trips in college, running with stock gears so revving considerably higher than desirable cruise RPM but engine entirely happy, unlike those State Cops.
  28. George/Maine
    Joined: Jan 6, 2011
    Posts: 949


    My flathead was overheating is 30degs weather could drive 10 miles.I replaced with Walker Raditor,no more problems.I had 4.4 gears and run about 55 mph guess about 3k.Your electric fan maybe your problem if turned on when diving could be blocking the flow.I checked the belt and mine is same way.
    Lets hear some info on overing boring and sleeves,and rust buildup in block.
    New SW gauge just hooked up 180 temstats,i,m running 190 driving think thats right.
  29. junk yard kid
    Joined: Nov 11, 2007
    Posts: 2,720

    junk yard kid

    I read the artical someone posted on t-stats on the first page. It says old thermostats are made to not be used with preasureised systems and that presureised systems use a different tstat. The OP says he used nos 1948 t-stats. I would want to use a couple of new units i tested with a temp gun on the stove in a pot of water.

    I believe t-stats make engines run cooler. Even though sometimes things work with out them. Ive watch the water and t-stat cycle so when the t-stat opens cool water comes in and shuts it leaving the water not moving in the radiator to cool off while the water n the engine heats up. Then repeats.
  30. we had a guy who put a BBC motor in a willys coupe and couldn't keep the thing cool..tried all the normal "quick fix" stuff,with no difference..Finally found out he had a WAY to much radiator for the car..Swapped the Rads out,problem went away..

    Flatheads are prone to cracks between the valves..Had a buddy who went thru 3 blocks before he found one that was rebuildable,for that reason..cracks..

    hopefully that isn't your problem,but worth checking the options.
    good luck .



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