2-blade or 4?

Walt Ebie

Walt Ebie

Senior Member
I'm about to replace my old water pump with a leakless variety and I'd also like to replace the fan. The car was restored about 1980 and they put on a 4-blade type at the time. It's still okay but just for the sake of going back to what was originally on the car, I'm thinking of replacing the 4-blade with a cast aluminum 2-blade. So I'd like to hear which type you prefer and why one may be better than the other. I would think technically the 4-blade would move more air than the 2, but that may not be true either. So what's your opinion?
 
My opinion is probably worth what it is costing you, that is the time to read it. I know of several failures of the four bladed fans. Haven't become aware of a failure of the two bladed, as long as it is correctly made of fit your water pump shaft taper. Try it on and make sure it can't wobble and I'm sure you will find that it moves as much air as your four bladed. I have read of studies that proved the two blades out perform the four. A failure of the four bladed will in all probability cost you some hood pieces and paint job, if you are lucky. My own failed fan took out the radiator core. Probably the cheaper failure. If it fails while someone is watching the engine run, well that could get rather messy.
 
this has been covered in depth often. A search will be revealing. Purdy Swoft has summed it up most elegantly along the way; look for his thread/posts.
Bottom line, the 4-blade is to be avoided, the blades can go flying, and the newly cast 2-blade aluminum is the best/safest way to go. The 2 blade alum moves plenty of air, not to worry

OK there are 2 ppl who type faster than I
 
I would go with the 2 blade cast aluminum. Buy a new one from a reputable vendor but still check it out. Some of the older ones were poorly made.

Charlie Stephens
 
FWIW: Many Model A Fan Experiences Over the Years.

Had one of the first, poorly fitting powder coated aluminum (2) blade fans with the incorrect inner taper when they first were sold.

After a few miles this aluminum fan sounded like three (3) skeletons vigorously tap dancing on a tin roof on a calm day.

Removed it, reinstalled the original steel (2) blade fan and threw the new aluminum fan with incorrect taper in the garbage.

Much later, after hearing that a taper correction was made, bought the modified new one from the same manufacturer and Model A parts place with the corrected taper.

After about 500 miles the new fan sounded like one (1) skeleton lightly tapping one (1) foot on a tin roof.

Found the powder coating under the fan shaft nut wore off whereby the fan nut loosened, the fan slid forward, and the fan was a slightly loose fit on the tapered shaft.

Removed all of the powder coating under and near the fan nut, placed a SS washer under this fan nut, and tightened the fan nut.

The skeleton(s) never returned ..... all is quiet and peaceful.

Over the past (20) years of Model A Forum messages reporting on fans, there were so many past sad stories and photos of Model A two & four blade steel fans coming apart and tearing up radiators and hoods.

In my humble opinion, installing a new aluminum (2) blade Model A fan makes just about as much sense as putting on a parachute "prior" to jumping out of an airplane ....... as opposed to jumping and trying to experience the joy of penetrating somebody's tin roof.
 
when you order one be sure to order the ever so handy fake water pump studs/ nuts. Supposedly allows removal of the water pump without having to disturb the radiator.
 
Minervas' four blade fan had some peened over pot metal?? type rivets & were loose enough to LET LOOSE!!!!
I replaced it with the 6 blade, PLASTIC fan. AND, don't LECTURE me, EVERYONE did that to me, about 6 YEARS ago!!
Bill Sorry
 
The general consensus is to go with the 2 blade fan - It is period correct and the fan is only needed when idling and driving slow.

The 2 blade satisfies most cooling requirements. The 4 blade has the potential of adding unnecessary drag.

If engine cooling is a concern for you, you may wish to consider a fan shroud as it will move air across all of the flues rather than just near the fan.
 
Here's a pic of the fan that is currently on my A. I'm guessing it was installed back in the 80's when my car was restored. It "looks" solid enough but I may consider replacing it. The replacements appear to have the fan and pulley as all one unit...
 

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99ZoomR said:
Here's a pic of the fan that is currently on my A. I'm guessing it was installed back in the 80's when my car was restored. It "looks" solid enough but I may consider replacing it. The replacements appear to have the fan and pulley as all one unit...
Click to expand...

Wow, that's an accident just waiting to happen.
 
To add to what H.L. wrote in posting #7, using a flat washer between the aluminum fan and the castle nut should be S.O.P. Otherwise, the nut digs into the aluminum fan hub as it is tightened and during operation, allowing the fan to loosen on the shaft. From the symptoms described in previous postings, I'd say those fans had been installed without that all-important washer.
If the new aluminum fan's manufacturer really wanted to help make his product accepted in the Model A community (and get rid of the horror stories about fan looseness on the pump shaft!) echoing the ones posted in this thread, he/she/it would include a special stainless steel washer with each fan sold. Add another 50 cents to the price, if profit is the main motivator for making the fan. A small slip of paper could be included explaining the need for the washer and a warning against leaving it out would cover the manufacturer's posterior.
A further suggestion: Try not to use a standard hardware washer because it is too thick and the circumference is too wide. It won't fit into the fan's recessed area on the front of the hub without a lot of grinding on the washer's edge. You won't be able to tighten the castle nut far enough on the shaft's threads to insert the cotter pin. Seek out a thin 3/8" I.D. stainless steel washer in your hardware store and use that.
By the way, I am also dead-set against using the four-blade fan - from bitter personal experience ($$$$$$$) and from sad stories related to me concerning damage caused by flying blades. Unless you have access to X-Ray equipment, you can't tell how rusted the area is inside between the hub rivets, the blades and the hub itself. These four-blade fans are a missle waiting to go off after 80 years. Some of the larger Model A tours won't even allow cars with four-blade fans to participate in their tours. What does that tell us?
Marshall
 
It would be interesting to know if the new aluminum two blade fans are in-balance or not. With the last 4 or 5 that I have been involved with, I have noticed where the blades have been ground on the back side, near one or both of the ends. A friend of mine and myself are building a balancing fixture to at least static balance the fan blade. Tom Wesenberg built up a neat looking balancing rig several years ago, now I was wondering if he found anything alarming with these aluminum fans ??
 
Are you guys talking about NOS 4blades or the new repro 4 blades. If your saying the new blades are bad then that is a whole new bag of air.

On the article that Tincup provided. Although difficult as it is to read it does show that the 4 blade definitely reduced temps over the 2 blade for both radiator temps and water temps by a large margin.

Based on the article, and only that article my vote is for a 4 blade. No, it doesn't look as cool as a 2 blade.
 
Here's a pic of the fan that is currently on my A. I'm guessing it was installed back in the 80's when my car was restored. It "looks" solid enough but I may consider replacing it. The replacements appear to have the fan and pulley as all one unit..
Click to expand...

This is the JC Whitney/Western Auto/PepBoys replacement fan from the 1950s & 60s.

I've had pretty good luck with these, even driving highway speed primarily in the Model A. I have three, have used two of them in active service, and have never had an issue.

Well, I did change out the "self tapping screws" on one of them for actual grade 5 bolts and lockwashers.

The same fan was also available in a 4 blade (2 propeller) version, which I don't have. A four blade version would double the loading on the four bolts so I might stay away from that one.

I don't own the aluminum fan - yet. But will probably go this way for appearance.

Joe K
 
One (1) sad, re-occurring Model A "Steel" Fan past problem was:

A. An old Model A steel fan develops a crack.

B. Some jerk fills the crack with liquid steel or other crack filler an carefully paints the cracked fan.

C. The jerk next sells it at a Swap Meet, on line, or wherever, along with his painted cracked axles, painted cracked carburetors, painted cracked wheels, painted cracked blocks, etc., etc.

D. The innocent, Model A owner/honest buyer buys this beautiful fan and installs it in good faith.

E. On a tour, 500 miles from home, the fan cracks further, becomes unbalanced, and one blade gets lodged in either the Model A radiator or hood.

F. Even today, similar jerk salesmen are everywhere selling "all" types of items ...... and still living happily ever after ...... some have had experiences with a few of these types who just love E-bay.

G. Just hope this helps some kind new, Model A gentleman/owner looking for a Model A fan.
 
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A good number of years ago I noticed a crack starting on the 2 blade fan and replaced it with an old 4 blade I had on hand. I keep a good eye on that fan and have not yet noticed any cracking.

I think i purchased an aluminum 2 blade but have not yet installed, it may be one of the older ones prone to splitting. I'm also not sure I could find it now.

As I understand it, the newer 2 blade fans are well balanced.
 
The aluminum 2 blade is the best and safest thing out there. Years ago many I tested had the blades out of parallel and some were out of balance a bit, but those problems seem to have been corrected. Every one I've seen and tested in the past 5 years is good to go.
 
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