four blade vs. two blade fan

ivoryjohn

ivoryjohn

Senior Member
My car doesn't over heat the way it is set up now and doesn't seem to use a lot of water even at highway speeds. However I am going to pull the engine to swap out a modified crank for an unmolested original with the slinger still intact.

While I have the engine out I want to swap out the water pump for a leakless one and replace the four blade fan with a two blade fan. I would also change the waterpump bolts for the look-a-like ones so if need be the water-pump can be changed without removing the radiator. I would also like to install a fan shroud while I am at it.

But....it ain't broke and it worries me fixing things that ain't broke. The car seems to be cooling just fine even though the deflector trough or tab inside the filler neck is missing, it doesn't have a fan shroud and has a four blade fan. Each of these conditions are suppose to spell trouble.

Does a two bladed aluminum fan cool as well as a four blade and does a fan shroud improve cooling? Also what is the reason the for the trough to deflect the water flow? Mine got left out by a radiator repair man. I've read the post that suggests making one and installing it to distribute the water evenly over the tubes. Seems to work well without it.

Please...one more question...the heavy duty water pump with the packing vs. the heavy duty water pump with the sealed bearings? Which?
 
A thorough test was done years ago between a four blade and a two blade fan on the Model A. It was found that the four blade fand didn't cool any better than the two blade. Packing vs. lifetime seal? No contest. Having used both, the lifetime seal has given me complete satisfaction without worrying about when should I tighten up the packing next and also having to clean up after the crud being slug around by the packing set up. On our 1930 Phaeton I stepped up and paid the price for the new aluminum fan and lifetime sealed water pump. I have found the fan to be perfectly balanced and I have no worry of losing a fan blad through the hood like I did with the A fan blade about 40 years ago. If a person is real careful on how he finishes the aluminum fan blade, hardly anyone can tell the difference in the new set up from a stock set up. I point it out to "A" owners and they usually are not aware of what it really is until I tell them that the fan/water pump is all re-pop. Step up to reliability.
 
Thank you Sssssss. I don't know if I should feel confident going with the two blade fan and sealed bearing pump considering your user ID name or not. I'm just saying....

Really thanks for a well written and thoughtful answer. I'm sure I can find plenty of additional information in our archives on the fan shroud and radiator trough in top. I guess I am just timid fixing things that are working fine. I will probably haul a fan, pump and the new style bolts around with me until I absolutely have to change a pump for the new.

Again, thanks for the answer. One last thing...I met a neighbor yesterday that lives two blocks away that has an unbelievable 1934 Roll Royce aluminum bodied limo sitting under a tarp. He had briefly pulled it out to go for a new muffler. He has had it since 1996. I can't believe I hadn't sniffed out this thing before now. Who knew?
 
From what I was told is the 4 blade fan was used on trucks and commercial vehicles for lower rpm. The only difference I've ever seen between the 2 and 4 blades is the sound. And if your radiator is cooling fine I wouldn't worry about it. When the car is up to operating temp place your hand in different spots on the front fins and see if there's a temp difference.
 
I agree with the "if it ain't broke..." theory. Now I have to ask, are you using a thermostat? A proper cooling A usually runs too cool so this might be a case of overkill, especially the use of a shroud. I just changed pumps to a leakless, greaseless style with the phony studs and had previously changed from a four blade. I love it! Why beautify an engine when the pump is going to sling crud all over it? Regarding the top tank baffle, its purpose is to prevent the incoming hot water from flowing over and out the overflow tube.
 
jkeesey said:
From what I was told is the 4 blade fan was used on trucks and commercial vehicles for lower rpm. The only difference I've ever seen between the 2 and 4 blades is the sound. And if your radiator is cooling fine I wouldn't worry about it. When the car is up to operating temp place your hand in different spots on the front fins and see if there's a temp difference.
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I was told that the 4 blade fan also robbed 7 HP over the 2 blade as well
is this true?
 
All of my A's have had the steel 4-blade fan. But of course, they can all be traced back to "commercial" use vehicles. 1st was an AA280A, the second was a Fordor, but had an AA engine in it, and my current is the Pickup in my avitar. I have had no problems, doubts or concerns over any of the 3.
 
I ran across this article a while ago.
 

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I'm not sure if it robs a whole 4 horsepower but its most likely not noticeable. It forces the engine to pull more air so it will labor it more.
 
as mentioned, the 2 blade cools better than the 4 and the plastic one too. The 4 blade was made post 31 for replacement and was never originally on an A or AA.. The 2 blade aluminum I have had on for 40,000 miles so far works great, looks close enough to the original to retain the original character of the engine compartment and is the least expensive fan of the choices. How can you go wrong?

BTW, the bolts that look like nuts will make removal a bit easier, but you still have to pull the radiator forward because of the impeller and shaft. A shroud turns a fan belt change into a big hassle, and a pump removal even more so, with little if any benefit to cooling. Ford dropped it from production because any benefit was probably not worth the expense.
 
BTW said:
I have the "bolts that look like nuts" on my '28 CCPU and I recently removed the pump assembly to replace the aluminum fan with an original later '31 steel 2-blade to enter it in Touring Class Judging at the Oshkosh MARC National Meet (recieved 488 out of 500 points). It was not necessry to move the radiator at all. Maybe I was just lucky. Don/WI
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Don/WI said:
I have the "bolts that look like nuts" on my '28 CCPU and I recently removed the pump assembly to replace the aluminum fan with an original later '31 steel 2-blade to enter it in Touring Class Judging at the Oshkosh MARC National Meet (recieved 488 out of 500 points). It was not necessry to move the radiator at all. Maybe I was just lucky. Don/WI
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the two blade is certainly far easier to remove than a 4 blade in any instance. I've seen cars with the fan nut almost touching the core, and others with plenty of clearance. I suspect it has to do with the core ( as some re cores are very thin and others are very thick) and the varying lengths of the repro water pump shafts. Then there is the position of the core within the frame, which varies as well depending on whomever re cored it. I had an original radiator in my SW at first. It had a lot of clearance but I still had to pull the radiator slightly forward to get the pump out. The odds of hitting the core with the nut while removing the pump is considerable, and a piece of cardboard should be placed between the core and fan to prevent that.
 
With a two blade fan you simply drain enough out of the radiator to get the water level below the neck. Then disconnect the hose and pull the radiator forward. Turn the blade horizontal and you can lift out the waterpump and fan as one piece. You don't even need the one piece bolts to do this.
 
I think a simply way to answer the whole 2 vs 4 blade debate is.

The "A" came from the factory with a two blade fan. Over the years the "A" was manufactured did this ever change? The answer is NO which suggests they did not find a problem with the design.

If its not broke, don't fix it.
 
What about a six blade plastic fan ? It was on the car when I purchased it . Any comments on this type vs. the other . Seems to move a lot of air . I read some where that the two blade original design moved 15% more air than the rest .Thanks
 
My car had a 6 blade on it when I bought it. It worked fine, never an issue. I had to pull the radiator to fix a leak so while I was there I pulled the water pump to put in the new bolts that allow it to be removed easier. Another club member mentioned how tough it was to get his 6 blade out so I compared the length to the new aluminum 2 blade and its about 1.5" longer. I put the 2 blade on the car. I like the look of it better and now I pull the water pump without messing with the radiator.
 
I have had the opportunity to work on a bunch of these cars. Every single time I have had to deal with a four-blade fan, it was cracking down by where the two pieces of metal are joined together to make the X shape. I have never found a broken or even cracked two blade fan.

For me, I will run the two blade fan. They work and have zero maintenance.
 
rustiny said:
What about the six bladed plastic fans that the suppliers sell? Anyone have any thoughts about those?
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My thoughts are they just plain look too out of place. I'm using an original 2 blade steel, but if I went with a repro it would be a 2 blade aluminum.
 
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