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Old 04-06-2021, 12:16 PM   #1
Pdgx
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Default Fan Blade orientation

Working on an over heating problem with a recent complete restoration (1930) - gets hot and boils over within about 10 miles @200į+ - and noticed the (4) fan blade looking like itís installed backwards - at least to me.

Looks like it is cupped backwards with the ribs to the engine ??
What is the correct orientation ?

Donít know if this will greatly improve cooling, but it looks wrong to me. Havenít found any manual or parts pic showing the orientation of 4 blade fans.
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Old 04-06-2021, 12:44 PM   #2
J Franklin
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Default Re: Fan Blade orientation

The fan needs to pull air through the radiator that is its only purpose. Maybe the timing is too retarded or the radiator isn't doing its job causing the overheating. Is the block clean of rust and gunk?
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Old 04-06-2021, 01:02 PM   #3
Badpuppy
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Default Re: Fan Blade orientation

Looks backwards to me - smooth side should be towards rear. Will pull air either way though. Aluminum blades are less likely to fatigue and fly apart; two blades are enough.
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Old 04-06-2021, 01:17 PM   #4
alexiskai
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Default Re: Fan Blade orientation

I concur that it looks wrong but it's not wrong enough to be causing you to boil over after 10 minutes. Especially because, once a Model A gets up to cruising speed, the fan is irrelevant. You can go for hours with no fan if you keep your speed up.
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Old 04-06-2021, 01:53 PM   #5
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Default Re: Fan Blade orientation

Well I flipped it and reinstalled it with the smooth, concave side to rear. Took the same route, corners, relative speeds and stops - and it didn’t exceed 200į or blow off.
While sitting stopped there is also significantly more airflow out the side louvers as well. (It does have engine pans)
So, (with out rehashing the 2,4,6 blade benefits - http://www.tulsamodelafordclub.com/m...-fan-air-flow/ ), it does appear it was installed backwards, and the smooth, concave side does go towards the engine.
The radiator and engine are virtually new from a professional engine rebuilder, and still flush cleanly.
This may not be the entire issue, but at least it is a significant improvement, and it doesn’t appear it will be dumping coolant on every run. Will see ....
Thanks for your input and verification. It just didn’t look right.

Last edited by Pdgx; 04-06-2021 at 02:05 PM.
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Old 04-06-2021, 05:30 PM   #6
Ernie Vitucci
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Default Re: Fan Blade orientation

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Good afternoon...Fresh Head Gaskets need to be re-tightened several times in order to hold the torque of 55 pounds or a bit more if you have a high compression head. The gasket will compress and thus the poundage will drop. At perhaps 2 hours, 8 hours and 20 hours running time, re-torque the head...just put the torque wrench on the nuts and give a firm pull until the wrench clicks...A loose head will contribute to warm running by allowing coolant to mix with the head from the exhaust valves...Ernie in Arizona
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Old 04-06-2021, 05:46 PM   #7
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Default Re: Fan Blade orientation

And the longer the engine runs the cooler it will as it breaks in! I would put a new 2 blade fan on. which pulls more air through the radiator !
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Old 04-06-2021, 07:03 PM   #8
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Default Re: Fan Blade orientation

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Originally Posted by alexiskai View Post
I concur that it looks wrong but it's not wrong enough to be causing you to boil over after 10 minutes. Especially because, once a Model A gets up to cruising speed, the fan is irrelevant. You can go for hours with no fan if you keep your speed up.
I'm not sure if I agree with you. If the fan is backwards it will try and blow air forward through the radiator stopping much of the incoming air and that will result in overheating at cruising speed.

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Old 04-06-2021, 07:28 PM   #9
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Default Re: Fan Blade orientation

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I'm not sure if I agree with you. If the fan is backwards it will try and blow air forward through the radiator stopping much of the incoming air and that will result in overheating at cruising speed.

Charlie Stephens
No, it will not blow air forward thru the radiator unless it is rotated in reverse (CCW from the front) - which it is not - it is still turning CW, it just was not using the curvature of the blades optimally.
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Old 04-06-2021, 07:31 PM   #10
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Default Re: Fan Blade orientation

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Originally Posted by Ernie Vitucci View Post
Good afternoon...Fresh Head Gaskets need to be re-tightened several times in order to hold the torque of 55 pounds or a bit more if you have a high compression head. The gasket will compress and thus the poundage will drop. At perhaps 2 hours, 8 hours and 20 hours running time, re-torque the head...just put the torque wrench on the nuts and give a firm pull until the wrench clicks...A loose head will contribute to warm running by allowing coolant to mix with the head from the exhaust valves...Ernie in Arizona
Thanks, I will check that in the morning !
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Old 04-06-2021, 11:01 PM   #11
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Default Re: Fan Blade orientation

PDGX,

If I were you, I would remove that fan ASAP.

What you have is a very poor replacement 4 blade fan. It has no strength in the blades close to the hub and over time, and in some cases not very long, the blades will flex just outboard of the hub and fatigue, crack and fail. When this happens, the blade will either exit thru the hood top, radiator or if you are real lucky, it will go straight down and not harm anything. I have seen several of these replacement fans fail and I would never have one on any of my cars. This fan also has a very poorly shaped blade that is very inefficient.

The replacement 2 blade aluminum fans that look like the originals seem to hold up very well and are very efficient.

The Ford Factory 4 blade fan that was used on the "B" engine was very well designed as far as the blade configuration was concerned and they have a reinforcing channel stamped into the part of the blades near the hub.

This is my opinion from over 60 years of experience in the hobby.

Chris Wickersham,
Techanical Director, Santa Anita A's Chapter, MAFCA.
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Old 04-07-2021, 12:09 AM   #12
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Default Re: Fan Blade orientation

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Originally Posted by CWPASADENA View Post
PDGX,

If I were you, I would remove that fan ASAP.

What you have is a very poor replacement 4 blade fan. It has no strength in the blades close to the hub and over time, and in some cases not very long, the blades will flex just outboard of the hub and fatigue, crack and fail. When this happens, the blade will either exit thru the hood top, radiator or if you are real lucky, it will go straight down and not harm anything. I have seen several of these replacement fans fail and I would never have one on any of my cars. This fan also has a very poorly shaped blade that is very inefficient.

The replacement 2 blade aluminum fans that look like the originals seem to hold up very well and are very efficient.

The Ford Factory 4 blade fan that was used on the "B" engine was very well designed as far as the blade configuration was concerned and they have a reinforcing channel stamped into the part of the blades near the hub.

This is my opinion from over 60 years of experience in the hobby.

Chris Wickersham,
Techanical Director, Santa Anita A's Chapter, MAFCA.
Agree with all of those points. Flipping the fan will not make it move air in the opposite direction.
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Old 04-07-2021, 06:34 PM   #13
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Default Re: Fan Blade orientation

The fan blades in your photo were indeed mounted backwards
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Old 04-07-2021, 08:06 PM   #14
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Default Re: Fan Blade orientation

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The fan blades in your photo were indeed mounted backwards
I think the problem goes deeper than that. By turning the blades over, they will still move air in the wrong direction. For that fan to draw air through the radiator, the motor would have to turn in the opposite direction. I figure they were made incorrectly and that the OP should take them back to where he got them. They are rubbish.
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