GT40 - Radiator Fan Shroud

[Randy V]

This is the radiator supplied with my RCR-40 #45.

It's a very nice single-pass radiator with two rows (very wide) of tubes that is reported to have ample capacity to cool a 600 HP engine.

Rather than just hanging the fans behind the radiator - I wanted to create a shroud to increase the efficiency of the fans.

The only "complaint" I have for this radiator is one that I have for literally any specialty radiator manufacturer::
Why in the world don't you make a radiator with provisions for mounting fans / shrouds?

In this case, there is a very narrow 3/8" lip at the top and a 2" wide lip at the bottom.

The top lip has about 1/4" of air-space underneath until the fins are encountered.

The bottom lip is the same - but there is a LOT more usable space of 1-5/8" wide at the bottom for which there are no fins/tubes directly underneath.

The mounting lips are well below the plain of the side tanks - about 1/4". I needed to do a couple of things here;
1) Build up the mounting lip surface to the same as that of the side tanks
2) Create a reliable surface to bolt the shroud to.

I used 1/4" thick x 1" wide aluminum for the bottom filler (you can see it in the top picture).
The top filler was made from similar material that was 3/8" wide.

Both filler panels were drilled and countersunk so the pop-rivets holding the fillers in place would not sit proud of the surfaces.

The shroud was made from 6160 T6 .080".

Retaining the fans::
The fans are drilled for 1/8" rivets as well as numerous radial mounts that are meant for 6mm bolts/nuts. I don't feel that rivets alone are sufficient to retain the fans so I opted to use 1 x 1 Angle aluminum (1/8" thick) to create a mounting ledge for the 1/4" bolts to mount the fans at the bottom/top. Note that I did not have any 6mm so I ground the heads on 1/4" bolts down to fit in the retaining slots.

The Top Plate is something rather special to me. It is a piece that I bought from an Auction at Richard Childress Racing about 10 years ago. It is an old radiator top mounting plate from one of Dale Earnhardt's Chevrolet Luminas.
Yes - I am also a NASCAR fan - please don't shoot me...

 

[Ian Anderson]

Randy

That is a very neat piece of fabrication work

Ian

 

[Chuck]

Randy: Be careful that your Dale Earnhart top plate does not get scratched by the Dsuz fasterner spring screws on the forward end of the front clip when the clip is slid on and off. The clearance is close. . . . . . been there . . . . .

I am not a NASCAR fan, but it would still be a shame to see such a nice looking piece get scratched.

 

[David Morton]

It would be interesting to see the cooling properties of your radiator with and without the shroud. To me, it looks as though you have blanked off quite an effective part of the radiator. But then again, I don't know a whole deal about these things and what you've done may work even better.
Dave

 

[Dimi Terleckyj]

Hi Randy

Nice work on the fabrication.

The only problem is that the shroud is too close to the cooling fins which effectively reduces the amount of air which could be drawn from the whole area of the radiator to only the area in front of the fans.

A minimum of no less than one inch or more is required for efficient air flow from all the surface area of the radiator.

Dimi.

 

[Julian]

Awesome work on the fabrication, however, like David and Dimi I would caution on the amout of closed area. At idle or slow speed the fans work more efficiently to draw air and your shroud improves cooling, but I know at least one Pantera owner who found with such a shroud that cooling was negatively impacted at prolonged high speed runs as overall forced air flow through the radiator was reduced.

His quite unique solution so as to keep the best of both Worlds was to cut some of the closed area out and reinstall the piecs on a simple pin hinges creating trap doors that opened under the pressure of the air at higher speeds.

 

[Randy V]

Randy: Be careful that your Dale Earnhart top plate does not get scratched by the Dsuz fasterner spring screws on the forward end of the front clip when the clip is slid on and off. The clearance is close. . . . . . been there . . . . .

I am not a NASCAR fan, but it would still be a shame to see such a nice looking piece get scratched.

Hi Chuck - Thanks for the warning.. While I have another plan for the retention of the nostril panel, I had not thought of potential clearance problems. I am also planning on making the front clip a Tilt-Clip rather than using the bobbins as originally designed so I'll make sure I clear everything as I design and fabricate the pivots.
Here are pictures that I just took this afternoon and it looks like I would have clearance, but I can see how I could have some interference while sliding the clip on/off the bobbins;

It would be interesting to see the cooling properties of your radiator with and without the shroud. To me, it looks as though you have blanked off quite an effective part of the radiator. But then again, I don't know a whole deal about these things and what you've done may work even better.
Dave

Awesome work on the fabrication, however, like David and Dimi I would caution on the amout of closed area. At idle or slow speed the fans work more efficiently to draw air and your shroud improves cooling, but I know at least one Pantera owner who found with such a shroud that cooling was negatively impacted at prolonged high speed runs as overall forced air flow through the radiator was reduced.

His quite unique solution so as to keep the best of both Worlds was to cut some of the closed area out and reinstall the piecs on a simple pin hinges creating trap doors that opened under the pressure of the air at higher speeds.

Hi Guys,

Thanks for the data points... I'll keep an eye on any sort of heating issues - but I've built them like this before and not experienced any. This, being a GT40, with less grill opening than I'm used to - there may be other dynamics at work... There is about 1/2" between the shroud panel and the fins. I can remedy and sort of blockage of flow quite easily actually. In the center portion of the shroud I can punch a 2" hole in the top and the bottom between the fans and place a rubber flap there to allow any positive pressure inside the shroud to be exhausted.

Onward through the fog....

 

[Howard Jones]

The one thing that will make the radiator work well is sealing the radiator opening with dams and rubber seals or however you need to, but ALL of the air that goes into the nose radiator opening MUST be forced to go through the radiator. No other outlets or leaks.

This may be the single biggest mistake home builders make with cooling systems. They just hang the radiator in the hole and hope it will work. It won't. Air flow will find the least restrictive way out of the nose opening once it enters. It will flow sideways around the front of the radiator into the wheel wells or over the top or under the radiator and into the area behind the radiator. This will pressurize the vary spot you want to be a low pressure area so that it will encourage airflow through the radiator and into the nostril area.

Seal it up so that you can't see light from anywhere except through the radiator fins.

As far as the shroud goes, I like the mounting points you made, but I agree with the others in that the panel is too close to the radiator. Move it back to 3 inches at the fan opening from a clearance of about an inch at the perimeter of the radiator. This will present a progressively less restrictive route through the air cooling track.

By the way I believe that the fans actually present a restriction above about a 100MPH. Any shroud will also increase the restriction in the air flow and as a result increase drag. In the end I'm not all that sure you need a shroud if the fans are point blank on the radiator and sealed around their perimeter so that air can only be drawn through the radiator fins.

 

[Chuck]

FWIW I never had any cooling issues with the RCR radiator without a shroud around the fans. Just curious if any one has ever had a cooling problem with these radiators? Of course mine is a modest 302, which may make a difference.

 

[David Morton]

Surely you are reading enough negatives to think this through a little bit more. Sooner rather than later it becomes part of the build and becomes more difficult
to change or modify. IMHO If it were me, I wouldn't use it. It doesn't really add anything. I used a double fan unit out of a Sierra Cosworth in my -40 and much like one of the posts above, when they are in the Sierra, there is no air path around the radiator - only through it and probably about 40% to 50% of the Sierra radiator is unhindered by fans - just free flow. We are talking about a saloon car that is capable of speeds that you will probably be struggling to achieve in your 40, and where at speed the fan is free wheeling as the thermostat has de energised it. I had the German produced Sierra 2.9L 4x4 - one of the best cars Ford ever produced and again it had a huge radiator but only a single fan with a viscous coupler. That worked very well - but again - no shrouds.
(Sierra 4x4 ? If they still made them I would have another straight away).

 

[Jim Cowden]

Question time.

The thermostat location is that STD RCR location.
It seems a long way from the engine.

Sorry Randy just curious.

Jim

 

[Randy V]

Question time.

The thermostat location is that STD RCR location.
It seems a long way from the engine.

Sorry Randy just curious.

Jim

Hi Jim,

The thermostat I'm using is from a BMW and I'll also using a forward mounted electric water pump rather than the original mechanical pump. This system is of my own design and based on other cars that I know and have built in the past. The coolant will recirculate through the bypass in the thermostat until such point in time that the heat brings the thermostat to open - thereby redirecting the hot coolant to the radiator.
There is more information about this system (although a slight layout change) on my website below..

 

[EGLITOM]

Randy

although i admire your nice fabrication, my thoughts are the same as Davids.

Fans are just for support. I rather have the cooler do the work as much as he can by itself. Therefore trying to maximise the flow through it by sealing the intake as much as possible and directing as much as possible air to the rad and also minimizing the backpressure by optimizing the outgoing airflow. Thats the reason i went with the single nostril panel and no shrouding on the backside.
I agree that the fans have to be sealed to avoid sucking in side-air instead of sucking air through the rad. I mounted them directly on the rad and sealing is achieved by 3mm rubber foam.

TOM

 

[(C)arlos]

Hi guys,
silly question, why don't you put the fans in front of the radiator? I have done this so I can modify the nostril to became a snug fit to the radiator. I assume this

- allows better airflow
- allows hot air doesn't heat the driving compartment as it all will leave the chassis through the nostril opening
- might adds some pressure to the front axel if you do the design correct of the nostril modification.



Am I wrong ?

Cheers
skeleton

 

[EGLITOM]

No

but this could also achieved with the radiators in the back and why should the airlow be any better ?

The reason for mounting it on the back is also that we have the AC condensor in front of the rad.


TOM

 

[Dalton Veitch]

I agree with the above sentiment re ducting all intake air onto the radiator, and utilising the fans only when stationary virtually, with minimal shrouding. I also prefer the idea of fans in front of the radiator. Try this test: on a hot day (ie. when you feel hot), try standing in your lounge with a fan in front of you blowing onto you, then try standing with a fan behind you blowing away from you. Much more effective in front of you, unless you add very airtight "shrouding" from you to the fan behind you. But shrouding, as has been mentioned, limits the air flow at speed. If you have an air conditioning condenser in front of the car's radiator, the fans can still be in front of that. It's good, and the condenser also needs air flow when you are stationary in traffic on a hot day.
My 2c worth.

 

[(C)arlos]

No

but this could also achieved with the radiators in the back and why should the airlow be any better ?

The reason for mounting it on the back is also that we have the AC condensor in front of the rad.


TOM

Ok, airflow might not be the best word here....Let's call it air-routing....Not only related to the radiator it self, rather then the whole flow through the car...I guess this becomes much better with the nostril flush mounted to the radiator.....
If you can achieve this also with the fans mounted on the back side, I would assume there is not much of a difference between front and backside mounting...A good argument of course it the air condition, If you have one ...:thumbsup:

cheers
skeleton

 

[Jon Briggs]

I think the best way is to mount the rad as air tightly as possable to the nostril, then mount the fans to the back of the rad, without any shroud. This presents the best frontal area of the rad to the cooling air, without any interuptions to air flow while moving. And if the fans are mounted flush to the back of the rad then max air flow can be achived when the fans are operational. This seems to be the way many sports car manufacturers do it, and how it's done on my TVR which is also a fiber glass body, and I hve had no problems with over heating.

 

[Randy Folsom]

Randy, it has been a few years since this post about radiators and air flow. Wondering what the current thinking is regarding mounting the radiator fans. In my case, my main concern is getting stuck in traffic and overheating. Thx much.

 

[Michael]

Thanks to Photobucket benevolence, I guess we aren’t privy to Randy V’s original photo array…

FWIW Randy F, living in FL with high heat and increasingly pervasive traffic, my biggest concern is the same as yours. As such, I’ve been reconfiguring my entire cooling system to preclude low speed issues. Well shrouded fans should be the most efficient means to alleviate low speed air flow through the radiator, so I fabricated an aluminum air box for that purpose. I made it a bit larger volume-wise to hopefully be less restrictive at higher driving speeds, and I configured it to be fairly easy to remove as an assembly for occasional track days. No idea yet how well it will function, as my motor is still out of the car and summer’s not here yet…

I do agree with what others have said about guiding as much air as possible into the grill opening is a good idea. Something else to attend to…