Vintage Mustang Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
112 Posts
Discussion Starter #1
My car has been running on the edge of over heating for awhile now. If the air temp is above 75°F after about 6 laps it will be on the edge and I have to back-off a couple laps to let it cool, and then only get a couple hard lays in before it creeps in the over heat range again. It hasn't ever boiled over but I'm aware of it so I keep an eye on the temp gauge and back off when I start to see a number I don't like. Three core alum radiator with double electric fans with shroud. 408w Ford around 500-550 hp. I've played with the thermostat which hasn't changed the situation much. 1967 Cougar body.
I've done a few winter projects to hopefully help it cool. I added two panels to the top of the core support down to the grille to help direct air flow thru the radiator. Added a front spoiler that might help scoop air up into the grille opening.
My question concerns the fan shroud. It's flat with the 2 electrical fan. My thinking is at speed it's blocking air flow thru the radiator and not letting enough air to exit the radiator. I have some hole punches and could add some 2" holes around the fans in the shro
IMG_1519[1].JPG
ud to allow more air to exit. Will this take away from the fan pulling the air thru the radiator? Would that modification help or hurt it cooling.
 

·
Registered
Joined
·
5,010 Posts
Do you have any hood vents? Some racers would raise the rear of the hood to let air, both heat and pressure escape. Do you have a heater and let it run like its winter time?
It might be an interesting experiment to remove the shroud and fans and let full flow try to cool it. Still several laps like that is as good as some late model Corvettes can do.
 

·
Registered
Joined
·
9 Posts
Cheap and easy: put a restrictor washer in the upper rad hose at thermostat to slow the flow of water through the radiator. Your coolant may need more time in the radiator to cool before making another pass in the block. A cross-flow radiator will definitely help. You have a conventional down-flow radiator.

Question for you: What is oil temperature doing? Is it mimicking water temp or above it? That may be a clue to whether the radiator is up to the task or not. Adding an oil cooler in front of the radiator may take some of the heat out of the engine. It also tends to pre-heat the cool air as it passes through the radiator. I vintage race my 1965 fastback with similar hp numbers and an oil cooler mounted in front of the rad. Mine maintains 200 water and 240 oil at 7000 rpm.
 

·
Registered
Joined
·
3,267 Posts
My question concerns the fan shroud. It's flat with the 2 electrical fan. My thinking is at speed it's blocking air flow thru the radiator and not letting enough air to exit the radiator.
I definitely think so. I would make some cutouts with flappers like this:
That will increase airflow at speed, while still sealing at low speeds/stopped so the fans will continue to draw air without bypassing the radiator core. As mentioned, you could just remove it all to test the theory first.
 

·
Registered
Joined
·
112 Posts
Discussion Starter #5
I currently don't have hood vents but I do run the rear of my hood slightly up to let air escape. I'm looking into hood vents and think I'll be adding some now. I do have an oil cooler installed and my oil temperature will reach around 250°F I'm sure this is helping keep my water temp somewhat in check. Otherwise I think my water temp would be higher. I did look into cross flow vs down flow radiator and found they're pretty much the same. Only slight advantage in cooling by having the pressure cap on the low pressure side on a cross flow. A cross flow wouldn't give me more surface area as I'm currently using the entire opening.
Going back and looking what's on Ebay I now see some of the fan shrouds with electric fans have louvers installed on the flat area on the shroud. Can't be much of a disadvantage at low speed If they're selling them now with louvers. I think holes wouldn't be any different then louvers they would both let more air escape thru the radiator.

Fan shroud.jpg
 

·
Registered
Joined
·
3,267 Posts
Hoods vents won't do squat if you're not getting airflow thru the radiator core. People really over-estimate the cooling benefit of hood vents. On race cars, hood vent are more for Aero drag reduction than cooling. As far as vents vs. flappers, just because "somebody sells it" doesn't mean its a well-engineered product, or suitable for your application. Those louvers are pretty small in total area, so it won't help as much as large rectangular holes with flappers. Any airflow louvers/holes allow at speed will be air allowed to bypass the draw of the fan when stopped.

If possible, before you spend lots of money, do some laps with the fans/shroud removed. That will tell you if there's an issue with restricted airflow.
 

·
Just some guy
Joined
·
20,231 Posts
The flaps exist one OEM cars for the same reasons. You need flaps because the fans can get where will draw air from the shroud vents instead of through your cooling. I'd consider the louvers unrestricted holes and I wouldn't have them. As to whether they would be a problem or not I guess you'd have to be a trained engineer with a million dollars or so of wind tunnel type equipment to know for sure. So the choice of flaps is the safer bet.

But just by looking, the shroud offends my eye. I can see airflow simply "bouncing" off the area of the radiator where the shroud behind is simply flat. Which would be severely restricting your radiator's potential performance at speed. It matches your complaint too. At speeds where aerodynamics are really in play it's running hot.
 

·
Registered
Joined
·
800 Posts
What size crank pulley, and what size water pump pulley? I dropped my crank pulley from a stock 7" to a 5.5" with a 6" wp pulley, and it was just enough to slow the high volume pump down, stop the cavitation, and allow it to cool. That little change made a very noticeable improvement.
 

·
Registered
Joined
·
4,520 Posts
It's probably that shroud. If you have a 24" radiator, switch to a Ford Contour shroud and fans. It's designed to allow air flow between the core and the shroud.
 

·
Registered
Joined
·
2,864 Posts
69, that shroud is the problem. Either dump it or cut it up and install some flaps. Louvers would not be enough. Don't raise the back of the hood, that hurts you, doesn't help you. The front spoiler and some ducting will help. LSG
 
1 - 10 of 10 Posts
Top