What is too hot for a flathead to run on a 90 degree day on the highway at about 2500 rpm? My 40 coupe with 53 merc motor runs about 205 after about 20 minutes. I have never let it go hotter than that, I just slow down and it will stay around 190. I run a 5 blade flex fan and 180 thermostats.
Cooling temp?
- Thread starter Stdblk40
- Start date
JSeery
Member Emeritus
"The normal operating temperature for a modern (1996+) automobile engine will fall between 200 and 250 degrees F. Smog equipment and computerized combustion control favor a 'hotter' running engine."
"Average engine temp would be around 195 - 205 degrees. The cooling fans come on around 210 degrees approx. The temperature will vary according to driving conditions, ambient temperature etc."
With an unpressurized coolant system the temperature has to be below the boiling point of water for the altitude. You would want a bit of a margin below the boiling point.
"Average engine temp would be around 195 - 205 degrees. The cooling fans come on around 210 degrees approx. The temperature will vary according to driving conditions, ambient temperature etc."
With an unpressurized coolant system the temperature has to be below the boiling point of water for the altitude. You would want a bit of a margin below the boiling point.
19Fordy
Well-known member
Have you checked those temperatures with an infrared gun just to double check what gauge is saying?
If it's not boiling your ok. Plus, keep an eye on those soft rubber radiator hoses to make sure they are able to withstand increased pressure with cap. From what I've read, "pusher" fans are not very effective.
The 8ba in my 40 has a 6 blade flex fan, Griffin radiator with shroud. On a hot day temp needle hits around 200+ in traffic, 180 on the road. As an experiment, I am going to remove the OEM drain pan below the radiator as i have been told that one of the problems with a 40 is that the hot air coming in gets trapped in the engine compartment. Maybe this will let more cool air in or let the hot air out easier.
Look here also for helpful hints.
https://www.fordbarn.com/forum/showthread.php?t=232691&highlight=radiator+shroud+40
https://www.fordbarn.com/forum/showthread.php?t=219724&highlight=radiator+shroud+40
If it's not boiling your ok. Plus, keep an eye on those soft rubber radiator hoses to make sure they are able to withstand increased pressure with cap. From what I've read, "pusher" fans are not very effective.
The 8ba in my 40 has a 6 blade flex fan, Griffin radiator with shroud. On a hot day temp needle hits around 200+ in traffic, 180 on the road. As an experiment, I am going to remove the OEM drain pan below the radiator as i have been told that one of the problems with a 40 is that the hot air coming in gets trapped in the engine compartment. Maybe this will let more cool air in or let the hot air out easier.
Look here also for helpful hints.
https://www.fordbarn.com/forum/showthread.php?t=232691&highlight=radiator+shroud+40
https://www.fordbarn.com/forum/showthread.php?t=219724&highlight=radiator+shroud+40
Last edited:
I have the factory splash shields on and the radiator pan. I also have a cover that tops the grill. This forces all air through the radiator. I will remove the splash pans and grill shroud, also check it with a thermo gun. The pusher fan is a panic device and never has been used. I have never got over 205, I just slow down, it normally operates at 170 - 185.
JSeery
Member Emeritus
So why are you concerned? With a 7 psi cap it is not going to boil over until well above 212. For every 1 psi of pressure the boiling point of water can raise 3 deg. And if you are running antifreeze, it is even higher. So 7 psi could increase the BP by +21 deg.
Attachments
Last edited:
It has been told to me by Alot of people to "don't get that flathead hot, they can't take it"
Nobody's ever said what hot is. I haven't had a problem, but don't want to have one either. Just was looking for a safe number from a group that have had experience with drivability of flathead engines.
Nobody's ever said what hot is. I haven't had a problem, but don't want to have one either. Just was looking for a safe number from a group that have had experience with drivability of flathead engines.
That flex fan may turn into an 'air dam' at higher engine speeds. They are designed to 'flatten' out as RPM's increase to reduce drag, but then they move little air. So air coming through the grille at highway speeds can be blocked by the flex fan acting like a wall.
JSeery
Member Emeritus
Well, you've been told wrong.
Flatheads are easily damaged by over heating, as in boiling over, 205 is not boiling over. The coolant temperature is not the issue, it's things like cavatation around the cylinders or low coolant levels etc allowing localized major over heating. That type of overheating can cause damage. If you are keeping the coolant level up and everything is working correctly the temps you stated are not a problem.If you are really covinced it is an issue, the only effective way to bring the temp down is to disassemble the engine and clean the block out, add high flow pumps, have the radiator cleaned out, etc.
Last edited:
19Fordy
Well-known member
Talkwrench
Well-known member
Though those temps sound fine as stated if you want to try something to get them lower and the motor has a been together awhile you might try a block cleaner by evaporust, I can’t recall the name of it atm. Thermocure I think Walmart carries it. I used the stuff in my 53 Merc and it’s solved all my overheating problems. Sorry if my grammar isn’t wonderful been up for 24 hours surviving on caffeine and hopes and dreams atm. College is wonderful...
tubman
Well-known member
I used "Rust-911" (works like to "Evaporust") in my last used engine and it worked very well. I ran with it in the engine until the engine got up to temperature, and then let it sit overnight. I then flushed it with plain water. I went through this cycle three times and it seemed to remove all the "junk" from inside the block. I have had the engine in my car for amost two years with no problems.Here are a couple of pictures of the inside of the block.
Attachments
You need to experiment to get the correct answer for your car. A fixed blade fan may work OK (they came new with one), but they sap fuel and power at highway speeds.
Try this: While keeping your head and hands out of range, rev the engine up to the RPM it sees at say, 70 MPH and see if the flex blades are flattened out. Also hold your hand behind the fan at idle, at about 1,000 RPM, and at highway RPM. Compare the amount of airflow at each speed. Obviously, if it diminishes noticeably, try a flex fan with stiffer blades, or the old fixed blade one. A fan clutch like modern cars would work, but I doubt there's room, and a lot of fabbing is needed.