2 Blade vs 6 Blade?

J

jeepguy1948

Well-known member
Does anyone have experience with the 6 Blade plastic fan? I had read an old article that said they were an upgrade but I’m having issues. There can be a long discussion about what can cause overheating but I would prefer to keep this thread only about the 6 Blade fan. Thanks
 
I swapped a 2-blade (metal) for the 6-blade (plastic) fan on the same car on the same day. The 2 blade did a noticeably better job, especially at lower RPMs. I think part of the issue is the plastic fan hub is so huge and the blades so small. Just a guess. I'm an electrical engineer, not an aerospace one.
 
Didn’t they do a study where they measured the cfm of each type and found that the two blade moved more air at low speeds but the six was better at higher speed? Also remember that, above ~35 mph, the fan does nothing.
 
alexiskai said:
Didn’t they do a study where they measured the cfm of each type and found that the two blade moved more air at low speeds but the six was better at higher speed? Also remember that, above ~35 mph, the fan does nothing.
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Colin, does it really matter? Remember that people will only believe what seems believable to them. :o :rolleyes:

I learned this a long time ago here when there was a so-called influencer here that argued with me publicly regarding how all LED lights needed to be focused and that I was wrong in telling people here how good the LED lights were using a Model-A headlight. Now some 10+ years later, that same person is all over social media bragging how good these LED light bulbs actually were for a Model-A being driven at night.
 
One major local club did a test measuring the air flow in mph , in front of the radiator , in front of the engine block , and to the side of the engine. The last two tests I feel are bogus because the air isn’t flowing through the radiator unrestricted , if one where too block the front of the radiator completely you would still have air being moved by the fans ! The 2 bladed fan had more air flow in mph than the four bladed or the six blade fan . At and above 35 mph car speed any fan is restricting air flowing through the radiator at a normal engine speed . On lower hp aircraft or boats they use two bladed propellers ! If more blades made them go faster don’t you think they would use them ?!
 
Jeep guy, with all due respect, if you are “having issues”, it makes little sense to isolate the discussion to one aftermarket component to help cure those “issues”. If all is working fine and you’re looking for an upgrade, yes, you’ll want to know if the 6 blade fan fits the definition of an upgrade. If all is not good, you are only asking for a “helper” to mask a problem …… or make the situation
“less not-good”.
 
It does make sense, I do not like threads that wander all over the place, I will ask more question after this one has been addressed. BTerry, I assure you that this is a legit question I do not have a bias one way or the other.
 
Big hammer said:
On lower hp aircraft or boats they use two bladed propellers ! If more blades made them go faster don’t you think they would use them ?!
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Not really. Simplistcally, aircraft use blade area to absorb usable horsepower within diameter limits. Low blade count is more efficient. Mitigating factors limit that to two. As usable power goes up, a propeller can utilize more total blade area...either by increasing diameter, width or count (or a combo thereof).

Multiple blades are often used on low hp, low speed aircraft. Typically this is used when reduced diameter or higher rpm is a critical factor.
 
I have plastic fans on both my Model A's. One has been in use since the mid-90's. The other was installed when the Slant T/S was restored in 2010. They have served me well and I don't worry about a fan blade going through my radiator or hood. Both cars have the Vintage Precision thermostat and run at 160-180 all year round.
 
I have a 2 blade fan on 2 of my cars and a plastic one on the other 2. I notice no difference between them but the comfort of knowing that the plastic one isn't going to break and damage the radiator (always in the most inconvenient place)
IMO, with or without a thermostat, I see no real difference.
 
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One of mine has a modern aluminum replacement 2-blade fan, and the other has a plastic 6-blade fan. Both run without overheating here in Texas. No thermostats, and regular 50/50 coolant mixed with distilled water.
 
TomInCologne said:
if my car was overheating, the fan is pretty low on the list of things to check...
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I agree. It's mostly in effect when you are not moving or moving very slowly. As soon as you are moving a few MPH, the ram air on the radiator does more than the fan does.

I have both aluminum 2-blade and plastic 6-blade fans on my cars.

I was recently able to swap out the water pump easily on the car with the 2-blade fan. All I had to do was extract the 4 water pump studs from the front of the head and the water pump swings out to the side.

To do the same job on the car with the 6-blade fan, I had to remove the radiator (and hood). That made it a much bigger, more involved job.

Given a choice, I'd rather have the 2-blade fan.

YMMV.
 
jeepguy1948 said:
It does make sense, I do not like threads that wander all over the place, I will ask more question after this one has been addressed. BTerry, I assure you that this is a legit question I do not have a bias one way or the other.
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And, ...respectfully, no one said you did. My point was that the bias often comes from false or incorrect advice you will receive here on some questions.


From my own personal experiences over the years, I concur with others that any overheating issues is likely not about being cured by switching to the use of a 6 blade fan in lieu of a 2 blade fan, however you stated you only wanted to discuss a 6 blade fan. My experience with customer's vehicles that have come in for service (-for overheating issues) has been the 6 blade did not correct their overheating issue. Personally I have never really viewed the 6 blade fan as necessarily an upgrade, but maybe others do, -so I did not respond directly to that as I felt that was not an answer you were seeking.
 
I have the 6-blade fan on my Coupe and the 2-blade fan on my Victoria. Both work well. The 6-blade fan is better balanced because its mass is concentrated at its hub.
 
Jim/GA, I have replaced two water pumps, by first taking the plastic fan off the hub and then taking off the water pump. The fan bolts are tricky to get at and I have small hands, but in both cases, I didn't have to remove the radiator.
 
If I was going to replace my 2 blade I would meet in the middle of this discussion and go with a 4 blade. And BTW, why do guys use pusher fans on their small block chevy. For more wind ?
 
oldford said:
If I was going to replace my 2 blade I would meet in the middle of this discussion and go with a 4 blade. And BTW, why do guys use pusher fans on their small block chevy. For more wind ?
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The aluminum 2-blade fans don't suffer from metal fatigue and cracking like the steel fans do. So I think they are safer. I've never seen one fail like the steel fans do (see photo -- that was a steel 2-blade fan).

Yes, the 4-blade fans are a compromise in number of blades, but they are still steel and I HAVE seen them fail and go out through the hood. I have also seen them slice up a radiator core in the engine compartment. I do not recommend them.

The 6-blade fan is plastic and I have never seen one fail. But they are hard to work around, and they don't "look right" under the hood, like the 2-blade aluminum ones do. They look too "modern".

Pusher fans mount to the front face of the radiator, so the air has nowhere to go except into the radiator. The Chevy guys have space in front of the radiator behind the grill for the fan and motor, so they put them there.
 

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Jim/GA said:
I was recently able to swap out the water pump easily on the car with the 2-blade fan. All I had to do was extract the 4 water pump studs from the front of the head and the water pump swings out to the side.
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It is even easier when you use those fake "stud" bolts for the water pump.
 
What about noise. Does the 6 blade fan make more noise. Or is it hard to tell with the noise the engine makes.
 
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