Okay guys. This thing has finally got the best of me. I have a 49 flattie and it runs perfect. Both heads run at about 190-195 temp and doesn’t ever smell hot. Here is the issue. If i run it at about 2200 rpm it never misses a lick. If i run 2500 rpm it will puke coolant out of the over flow. Still dont get hot. Does not matter how full or low the radiator is. Have tried everything from a 4lb cap to a 12lb cap. Has a walker radiator in it and it is newish. Any thoughts other than an overflow?
Overflow canister is your friend. I run my flathead with no thermostats. No need for them where I live.
lucky: I have a 239 cu. inch 53 Ford 8BA in my 40 Ford along with a 1999 Walker Cobra radiator and a 10 lb cap. My pumps are 8RT truck pumps as they fit the motor mounts in my 40. Am using DEXCOOL coolant 50/50 with distilled water. No thermostats. Temperature is about 180 when driving on open highway. Gets hotter in traffic and boils when the TEMP needle covers the H . Just for the heck of it, try removing your thermostats. I also am using water pumps rebuilt with different impellers. Do things change if you drive without the rad. cap tight? Here's more info. on the pumps. Water pumps - The Ford Barn Two more thoughts. When you fill the radiator only fill it with enough coolant to just cover the top of the internal radiator fins. That way the coolant can expand without overflowing. No need for an overflow tank. Don't fill the entire top tank with coolant. Also, buy an infrared temp. gun and take readings as your engine warms up to see if the radiator is cooling the coolant. Rad. should be hotter at the top. Harbor Freight has temp. guns. Also, look here for lower prices than Harbor Freight. Amazon.com : infrred temp laser gun
What does "newesh" actually mean? My 47 Ford would puke out coolant if I drove over 45-50. It would push out enough to eventually overheat. I pulled the radiator that looked really good inside. The radiator shop found it to be about 70% plugged in the lower tank. Realize that plugging 1/2 in of a tube cuts off all the flow in that tube. I worked at a dealership that did some radiator work. Many plugged radiators looked really good inside but 1/4 to 1/2 inch of a good percentage of the tubes were plugged. If you can find a radiator shop with a flow bench they can test it, but that isn't likely anymore.
Head gasket, my 255 did the same until I torque the heads to 75 lbs. original heads and bolts. I use a 7 lb. cap.
Jim brings up a good point. Is the 2500 rpms, spinning with no load, or running down the highway under load? If under load, it is most likely head gasket related. I.E. the heads are lifting up under the higher combustion pressures experienced under load and breaking the gasket seal. Combustion gases enter the cooling system and manifest themselves by pushing coolant out the overflow tube. Long winded engineering anecdote: At a previous company I worked for, we had developed a particularity strong V-Twin engine and stuck it in a chassis that was wholly unprepared for that much power (this should sound familiar to all of us hot rodders). Because of this, the engine had a very low duty cycle because very few riders had the stones to hold it at WOT for more than a few seconds at a time. The next chassis we stuck that V-Twin into was much larger and heavier, causing the duty cycle to increase significantly. In the new chassis. we quickly discovered that the cylinder heads had a fatal design flaw. The heads were not stiff enough to maintain proper clamp on the head gasket under extended periods of WOT. The head gaskets would burn quickly, and the thing would start pushing gases into the coolant, even at idle once the gasket was toast. Of course we got to the root cause a few days before the first units were scheduled to go down the assembly line. Management decided to push forward with production to meet sales quotas and "Because it was just an engine swap, right???" Call NHTSA and Que recall in 3, 2, 1.....
Flathead Fords are a rust factory if you don't use some kind of rust preventer. I always preach to not ever run one of these with straight water in the cooling system. Ever! Run 50/50 antifreeze with a can of rust preventer added every year. Your engine could be releasing rust flakes (little chunks) from inside the block. Very common with these. This is at it's worst if the car has been sitting in storage with no coolant in it. These will plug the radiator tubes pretty quickly. You should take the radiator to a shop to have it rodded out and back flushed. Now, another thing that I've found is cracks inside the block can, especially around exhaust valve seats can over pressurize the cooling system and blow coolant out the overflow. Also, I found out by accident that a radiator with no baffle in the top tank can cause the coolant can send a sheet of coolant across the cap and pressure can blow it past the cap gasket and out, especially with block cracks. I found that out by leaving the cap off it would flow around the fill hole and not across it and would not lose anything. Not the greatest idea to run a really clean system without thermostats. The coolant can zip through the radiator before it gets a chance to cool.
I don't know much but I do know if it runs around town and doesn't overheat but does at higher rpm down the hiway, the radiator is either plugged or of insufficent size. Lippy
This statement gets repeated over and over in automotive circles and is very misleading at best, and completely incorrect at worst. The correct statement is: As the mass flow rate of the coolant increases through a radiator, the temperature difference between the coolant inlet and outlet decreases, BUT the heat transfer rate remains the SAME. In other words, if your engine maintains 205 degrees on an 85 deg day while driving 60 mph, and your engine has a water pump that will flow 10 gpm at that given speed and RPM, hypothetically you may see a 30 deg temperature difference between coolant at the radiator inlet (205) and outlet (175). If you remove the thermostats and now have 20 gpm flowing through the rad, the temp difference will drop to 15 deg (205-190), but the engine will still maintain 205 deg on that 85 deg day. Engineering Explanation: The heat rejection rate of a radiator is dependent on the design (fin pitch, core thickness, air flow rate, material type, etc.) of said radiator. That means the heat rejection rate is essentially constant. The only thing the fluctuates is the ambient air temp, air conditions, and air flow rate (dependent on vehicle speed). At a given set of external conditions, it is constant. The heat rejection rate to the air has to be equivalent to the heat transfer rate from the coolant. This is otherwise known as the 1st Law of Thermodynamics, and is non-negotiable. The coolant heat transfer rate only has 2 variables, the mass flow rate and the temperature difference across the rad, and is defined by the following equation. Q = Cp(m)(T1-T2) Cp is a constant (dependant on working fluid, ethylene glycol, water, etc.) m = mass flow rate of coolant T1 = Inlet Temp T2 = Outlet Temp Since Q and Cp are constant, If m increases, (T1-T2) must decrease and vise versa.
Okay guys. I guess i need to give a little more back story. Radiator is about 3 years old so not new. Motor was built by H&H. The car only pukes when driving under a load above about 2500rpm. I have tried an infrared gun and it is a difference of about 40 degrees from inlet to outlet at a warm idle. No thermostat in either side. Going to check head torque and see what it is at temperature. Thanks for all the input. Also gonna call Johnson’s tomorrow and see what they say since they bought Walker out. Maybe they can test it.
A guy, a mechanic long ago told me, (don't know if it's true) that an oil or trans cooler will not make it run cooler but it will take it longer to get to the max temperature. But in time it will still get to the same temperature. Lippy
Simple test. Take the rad cap off. Run the motor up to temperature. Up the revs to the critical rpm and look at the coolant level. If it suddenly goes up the water pumps are cavitating. This is due to the restriction in the rad being too high and pulling a vacuume. If this is the case a simple fix is to run thermostats, that will restict out flow and reduce the risk of cavitation. Its a very common problem on As and early flatheads with suck through water pumps. Much rarer in later ones like yours.
are you running an aluminum radiator? How long have you been using the DEXCOOL? In time DEX and others like it will destroy a brass/copper radiator. I don't know the full science off the top of my head but there's a good bit of info online that's worth a space in our memory banks. The Cliffnote version is that the acids are detrimental to the solder bonds in the tanks and cores as well as the brass. It is good for uncommon metals like iron blocks and aluminum heads, but doesn't like brass/copper/lead. A friend lost a very expensive honeycomb core to DEXCOOL about a dozen years ago. Another put a similar product in a Packard (I forget the name but a waterless coolant) and it separated his oil cooler core in a year. The radiator had 2 leaks and was serviced and tested prior to. Look it up, this should not be a shrug it off thing, brass radiator, stay old school.
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