cooling question

[Falcon67]

>.i dont think that is his problem.they are rated to 750 horse so on a 600+ engine i think its fine

You don't rate radiators for HP, that's marketing BS.  Besides, you're not making 600HP putting along at 65 MPH.  The 4 cores are too thick for use with electric fans.  Go look at any modern car and tell me what you see - almost no fixed engine fans aa zero copper/brass core radiators.  A 2020 Shelby makes 760 HP and I can guarantee without looking it doesn't have a 4 core radiator in it.


Two cores, 31x19, OEM fans, keeps 500+ HP under 200 at full throttle with only the 30 GPH water pump running. 

[babybolt]

Cooling in these Mustang has always been a challenge with high horsepower engines.

The problem, I think is getting the airflow out of the engine compartment.  The shock towers tend to block the flow around the engine.

A front spoiler helps.

Your 4 core radiator probably blocks airflow.

Years ago I asked a Ford cooling engineer about crossflow vs the standard 69/70 Mustang top and bottom tank with the inlet/outlet at opposite corners.  He said there is only 1 or 2 degrees by changing over to a crossflow.

I've seen several 69/70 Mustangs that came from Nevada, and they had cut out openings the side aprons ahead of the shock towers.

Ceramic coating the inside and outside of the headers helps.

Somewhere around 10 to 15% or more of engine cooling is airflow around the engine and back under and around the transmission.

A separate oil cooler out front could help too.

The front end design of these cars, and really all cars of these years is not very efficient at directing the cooling airflow through the radiator, a bunch of the flow is lost in the large cavity behind the grille and the resulting open areas behind the valance panel/ahead of the tires, etc.

[1967FEGT]

I don't know if this information will be of any help.  I have a Dual Quad 427 that produces about 600 HP. I have the factory 24" radiator with a 3 row core, shroud, and C6OE-F fan and Thermostatic clutch. Edelbrock water pump. I am using the Stewart EMP 180 thermostat.  It doesn't overheat even in 100 degree weather and stop light hopping. I drive spirited but I am not driving at the strip. The temperature comes up a bit right after I get off the freeway then quickly settles back down about 10 minutes. I don't have air conditioning.. Yet. I'm restoring an original ford unit. I don't know what to expect, especially with the inboard headlamps after I install the condenser.  It seems to maintain quite well being run as designed.

[Falcon67]

>Cooling in these Mustang has always been a challenge with high horsepower engines.

True that.  You can fit a 19" tall aftermarket unit in a 69/70 but the width is a challenge.  The 31" wide unit I have drops in my Falcon easy and clears the side rails.  Just trimmed the core support a bit to match the core width.  Not so much room  in a Mustang.  The 70 had a 26" wide unit, IIRC.  That and a couple of cheap eBay 12" fans on a formed shroud with a Flowkooler pump and the bitty Moroso drive motor was good enough at the drag strip.  The car would stage at 180 and come back from an 1/8 mile pass at 200~210 then cool down in just a couple of minutes. 

[1967FEGT]

>Cooling in these Mustang has always been a challenge with high horsepower engines.

True that.  You can fit a 19" tall aftermarket unit in a 69/70 but the width is a challenge.  The 31" wide unit I have drops in my Falcon easy and clears the side rails.  Just trimmed the core support a bit to match the core width.  Not so much room  in a Mustang.  The 70 had a 26" wide unit, IIRC.  That and a couple of cheap eBay 12" fans on a formed shroud with a Flowkooler pump and the bitty Moroso drive motor was good enough at the drag strip.  The car would stage at 180 and come back from an 1/8 mile pass at 200~210 then cool down in just a couple of minutes.

As for the core, there are no 26" cores in 67-70 FE or AC cars. The original 67 core is actually 23" and the 68-on is a 24" core. No one is reproducing the 67 core so it forces a change to the 68 radiator and a change in bottom mounts.  I agree with you, managing heat in many hot climates is difficult.


Not everyone is drag racing or is going to cut up a car for cooling.  Especially original FE cars or Shelbys.  The cars didn't overheat new. So there has to be a formula here to resolve the issue.

[cjshaker]

Not everyone is drag racing or is going to cut up a car for cooling.  Especially original FE cars or Shelbys.  The cars didn't overheat new. So there has to be a formula here to resolve the issue.

Out of the factory, they were pretty conservative engines compared to what most people do today. Everybody wants to squeeze horsepower out of a big block, and horsepower=energy=heat. Still, I agree there is a formula for beating it.

There's plenty of room in a Mustang for a much wider radiator, but you do have to cut the support area up, and most people (me included) won't go to that extreme. I have a stock type brass radiator, edel pump, 180 thermostat with a flex wide blade fan and factory shroud. 500hp 427 in a Mach 1 with no scoop. It's never overheated, but when I got stuck in traffic on a 90* day during Drag Week, it did go up to 210*. I was about to pull over because I admit it was making me nervous, but that was when the traffic started to flow and the temp dropped immediately. It usually never goes over 200*, or 190+ at speed.

[Falcon67]

>Not everyone is drag racing or is going to cut up a car for cooling.  Especially original FE cars or Shelbys.  The cars didn't overheat new. So there has to be a formula here to resolve the issue.

300HP = 150 lbs/hr = 22 gallon/hr x 114,000 BTU/gallon = 2,514,612 BTU/hr x .333 (about 1/3 lost into the cooling system) = result 837,366 BTU/Hr that the cooling system has to disperse.  Even at 100 HP that' figures to 279,132 BTU/Hr.  Over bores allow more heat from combustion into the water jackets, higher compression + more timing equal more heat, etc. 

A 2000 sq/ft house in Houston, single story, average insulation, summer needs about 57,300 BTU/Hr cooling. 

[cammerfe]

I saw an evaluation of the power needed in a test car while running a ten mile loop while being evaluated. As I remember, an ordinary car, at about 65 MPH, takes about 50-60 horsepower to keep it at speed on a level road in regular conditions. Almost anything beyond that is simply excess that is available to make the car accelerate. FWIW

KS

[1968galaxie]

I am joining the choir thinking the thick 4 core is certainly part of the issue.
I have never had an overheating problem.
I am using the factory stock 390 2V radiator in my 68 Galaxie.
The engine is now a 501" BBF over 700 hp.
Mechanical Flex fan used.
Street cruising the temperature stays at 185 on cooler days (75F) 190 when 80.
In a hotter climate perhaps I would have an issue?

Perhaps it may be worthwhile to find a stocker rad and experiment a little.

Good luck!!

[Hemi Joel]

Does the fan shroud block air flow when going down the road? I never understood those shrouds that are just about flat over the back of the radiator.

Anyone who thinks you can improve cooling by slowing down the water flow needs to move into the 21st century. That old wives tale was scientifically disproven years ago. If that theory were true, then you could also improve cooling by slowing down air flow, so the air would have more time to absorb the heat. So try running your fans on 6 volts to cool your engine better.

[My427stang]

Does the fan shroud block air flow when going down the road? I never understood those shrouds that are just about flat over the back of the radiator.

Anyone who thinks you can improve cooling by slowing down the water flow needs to move into the 21st century. That old wives tale was scientifically disproven years ago. If that theory were true, then you could also improve cooling by slowing down air flow, so the air would have more time to absorb the heat. So try running your fans on 6 volts to cool your engine better.

Agree 100% and give you a big AMEN...however, restrictors on the outlet side can be useful for different reasons, depends on the system, but can force water in a better path through the block minimizing hot spots, and in some cases, reportedly will stop intermittent pump cavitation. 

I am not sure I buy it as much as I used to, seems that the heads would provide plenty of restriction to maintain water pump head pressure, but I have seen Rat Chevies act funky in Las Vegas heat with no thermostat in them, then work perfectly well with a restrictor or thermostat, but as you said, it's got nothing to do with speed of the water through the radiator.

[sixty9cobra]

All good points. I think I will add a spring in the lower hose. I'm not going back to a mechanical fan again so maybe better fans. Worse comes to worse a bigger radiator. I would just like to get it right. I never believed the to cold of a thermostat thing 180 160 same thing in my book.

[fryedaddy]

All good points. I think I will add a spring in the lower hose. I'm not going back to a mechanical fan again so maybe better fans. Worse comes to worse a bigger radiator. I would just like to get it right. I never believed the to cold of a thermostat thing 180 160 same thing in my book.

I hope the spring helps,it cured mine and i had the same symptoms as you.like i said my 4 core rad heats up in less than 5 minutes,maybe quicker,and thermostat kicks in ,and it goes straight to 180.  190 at a long red light.sounds like normal operation to me.  GOOD LUCK,i hope that spring helps you too.

[Cyclone03]

It’s the fan shroud.......
I had the SAME problem with those fans .

[sixty9cobra]

 the fans will come with a new shroud of course .I think I will go with the Spal fans I need to figure that out yet I wonder if I drill Large holes in the shroud as a test and take it on the highway will it prove anything.