Building a Custom Fan Shroud: Pic by Pic

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autoxcuda

autoxcuda

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Building a Custom Fan Shroud: Pic by Pic

I have a Champion 4 core 228221; radiator that has performed well in my new 416 stroker small block. I've put 3458 miles on the motor in 1 ½ years and driven a few times 80 miles @3700rpm to/from Willow Springs Raceway racing 60 laps/150 miles going about 130 mph @ 5800 rpm on straights. Radiator looks great inside, no rust, and no measured electrolysis. I run distilled water and Justice Brothers Radiator Cooler (RC/22P) and Justice Brothers Cooling System Protector ( CSP/1P). No major cooling problems, but I don't run a fan shroud.

Once in 88 degree heat I got stuck in road construction barely moving for 20 minutes. Motor got up to 215 degrees. The fan by itself just could not pull enough air without the car moving. Time for a shroud.

When we first built the motor, the Champion upper radiator hose mounted way too close to the center and hit my 5 blade MP fan kit. So I cut off each blade of a 5 blade and made a fan. The car still performed pretty darn good with a skimpy looking fan and no shroud. I run the short Jaguar fan clutch (Hayden #2765) because of the thick radiator and 70-up taller aluminum water pump.

The upper hose inlet tube had to be moved outward to fit any fan shroud. Radiator Works in Northridge, Ca did that and added a aluminum tab on top to help attach a shroud.

The factory 68-69 and 70-72 V-8 shrouds needed cutting to end up with a marginal shroud. So I traded some parts with Troy and he said he'd make me a shroud if I helped.

Here's the pictures that tell the story.



That aluminum angle is 1/16" thick and 3/4" by 1/2". 48" long piece. The 20 gauge aluminum sheet was $21.75 for a 24" x 48" piece.

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We put these on the existing Champion holes. But the aluminum was too thick for them even after I bent them out some. So we thinned the aluminum out some and also made the shroud end rails fit more flush.

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When the radiator was still in the car I marked the centerline of the water pump translated to the radiator itself. This way we would know where to start the center of the fan shroud opening later. I also had the upper shroud tab welded onto the radiator along this centerline.

We added foam to make a tight seal and to protect the shroud from rubbing into the radiator tubes/fins.

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Foam detail

Side rail angles not installed yet.

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The optimum hole diameter for shroud take the fan diameter and add 10% of the fan diameter. So for my 16" fan I added 1.6" to 16" and cut my hole at 17.6".

The optimum depth of the shroud is when the pitch of the fan blades are showing 1/2 in and 1/2 out of the shroud.

That info came from a past employee of a large automobile and industrial radiator manufacture explained to me the design of a fan shroud.

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Troy cut the hole with a handheld jigsaw. The tape is so the aluminum doesn't get all scratched up from the jigsaw bouncing on it. I have a little hand held notcher. Neat, but would have taken me forever to cut something this large.

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Here's the detail of the foam on the bottom of the shroud.

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I wanted a durable finish on the shroud that didn't need the maintenance of bare aluminum. So I painted it VHT wrinkle paint baked in an oven. I can run my fingernail against this paint enough to file it and it will not scratch.

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The fan for my system is very small. Like I said before it's a MP 5 blade fan cut down 1" so it would clear the inlet tube and be lower than the top of the radiator (don't cut my fingers off). This was done 1 1/2 years and 3458 miles ago.

The 1" cut really takes a lot of meat off the fan. Five 1" cuts stacked on the right next to the C-clamp pictured below. I'm really shocked it cooled so well without the fan shroud. I guess I could say it's low drag for increased horsepower.

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Here's the anorexic looking fan mocked up with freshly painted shroud.

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This shows the idea of the fan blade being 1/2 in and 1/2 out of the shroud

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Here's a picture of the fan shroud installed.

The JAZ over flow bottle on the right has a valve so you can drain it when and where you want. Not that its ever had anything overflow into it of significance.

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I refilled the radiator with distilled water and Justice Brothers Radiator Cooler (RC/22P) and Justice Brothers Cooling System Protector ( CSP/1P) to give me the best cooling and resistance to electrolysis.

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So I got it all together and tested it. It was 92 degrees in my garage when I started it up.

I figure if I went this far, I was really going to test it. I've been a S-O-B to this car for 19 years, why should I stop now ....


I let it idle for 25 minutes not moving it an inch in the garage!


The front of the car was 1 1/2 ft from my washer and dryer. So no wind to help it. Even with an open garage door, after 25 minutes my eyes would tear up if I stayed in there too long and the car raised the temp in the whole garage to 98 degrees.


1) After 10 minutes idling, temp measured on heat gun was 160 deg. at the temp sender.



2) After 25 minutes idling, temp measured on heat gun was only 203 deg. at the temp sender. Turned it off and no boilover whatsoever. I didn't think that was bad given the extreme abuse. It was a fricken nauseous sauna in there.

I think it did really well for such an extreme test! :D :D :D

Here's a picture showing the suction of a paper towel on my grille at idle and the ambient temperature there.

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Read more about this article here...
 
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Lookin good. I've been thinking of building meself a brake. Going to have to do something on this order, myself.

My former (Lennox) employer can run me off a strip of notched scrap, for a fan housing. All I'd have to do is cut the center hole, cut the strip to length, and bend all the tabs over, then rivet or weld
 
Oh how I would love one for my Champion with Dual fans ;)
 
Do you know what your clutch is off of? Mine is a used one I had, and is VERY close to the rad
 
67Dart273 said:
Do you know what your clutch is off of? Mine is a used one I had, and is VERY close to the rad
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Is the shortest I know of you can get new: Hayden #2765. It's originally for some Jaguar application. It's still only about 1/2" from my radiator. If I ran a cast iron 69 and down water pump, there would be more distance.

Hayden #2765 (if you google it you may get better specs on it):

Shroud 15.1.JPG
 
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Thanks very much. I'll check the one I have, I'm sure mine is a little longer. I think it came off a van. I also shortened the blades, just made a center "pilot" for the shaft socket on the rear, and took a big set of dividers and scribed around the blades.

My rad is a lot thinner than yours (stock 273) and the clutch is STILL only about 1/2" away.
 
67Dart273 said:
Thanks very much. I'll check the one I have, I'm sure mine is a little longer. I think it came off a van. I also shortened the blades, just made a center "pilot" for the shaft socket on the rear, and took a big set of dividers and scribed around the blades.

My rad is a lot thinner than yours (stock 273) and the clutch is STILL only about 1/2" away.
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I thought about scribing it like that too. But my friend Troy (ns1rm21 here) had the great idea of just putting 1" wide masking tape at the end of each blade. Works perfect. Run the motor up to 5800 rpm and 130mph down the front straight at Willow Springs Raceway!
 
Very good info to know as I just recieved my Champion 22in. 3 row radiator today for my 70 Dart. I hoping that I will able to run it without a fan shroud for a while till I figure some type of a fan shroud. The fan that I have is a 7 blade thats almost 18in tip to tip. But its not a clutch style. It bolts directly to the water pump with a spacer. Hoping to have it together tomorrow or Friday.
 
Rice Nuker said:
That was a great read, thanks much! Good trial testing.
How come you cannot find a fan to fit your shroud?
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The radiator sits too low and I didn't want the fan to stick up 1" over the top of the radiator.

I first cut the fan to 16" dia because the top neck of the radiator was too close to the fan. I think the ones ChallengerGary sells now for 70 A-bodies (I have the aluminum water pump) now have the top neck moved over from the factory.
 
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