3 blades verses 6

[3739ford]

Hey Guys,

Wanted to see if there would be an advantage/need of putting the 6 blade fan in place of the 3. I have no idea if the 3 blade would be just fine that is why I'm asking. This is a 276 in. with skip rebuilt water pumps and shewman 180 degree thermostats. I was planning on using a shroud also. Now would be a good time since I can get to everything easy and I could cut apart and mount. I know I could just buy a flex fan, but no fun in that.

All responses appreciated both positive or negative and both informative and not.

 

[ford38v8]

The 6 blade fans sound like an airplane taking off. They also chew up your horsepower to make that noise. The 180 thermostats are good, and the shroud is by far the best thing you can do.

 

[Kurt in NJ]

That 6 blade fan looks a lot like the crankshaft mounted fan from like a 40 would have

 

[19Fordy]

Use the stock fan. Henry knew best. Just for the fun of it you could do a Google search on fan design regarding number of blades and blade pitch to see which moves the most air at idle and at speed.
I found the following re: ceiling fans.
"When a fan has fewer blades, there is less drag on the motor and it can go faster and move more air more efficiently. This results in much more airflow and will create a better wind chill effect, making your space feel cooler."

 

[3739ford]

I have no idea what the 6 blade fan fits it is in my pile of "don't know" flathead parts. I suppose I could go with electric fan, or leave it like it is.

http://www.griffinrad.com/tips.php

 

[flatford8]

I’ve been looking for an “at speed” vibration in my ‘50 Fordor. It had a 6-blade flex fan on it. I swapped it out for a 3-blade stock fan and noticed no over heating issues and it was quieter than before.....Mark

 

[aussie merc]

different fans mounted in different locations doing the same job we need to look at the whole picture . both work otherwise they wouldn't have made it into production . the crank mounted fan needs to be bigger as only 2/3rds of it actually aline with the core so even if its not obvious there's always a reason

 

[Charlie ny]

3739,
The shroud man, with the 3 blade fan. Fit the shroud close to the fan diameter.
Charlie ny

 

[51 MERC-CT]

Hey Guys,

This is a 276 in. with skip rebuilt water pumps and shewman 180 degree thermostats.

All responses appreciated both positive or negative and both informative and not.

If you are using Skip's pumps with the improved impeller it is my understanding that he says not to use thermostats with his pumps in the instructions that come with them

 

[19Fordy]

I use Skips pumps and the early MCF heads which were designed not to use thermostats.

 

[3739ford]

Had the water pumps done a year ago and don't remember getting instructions with them. Great info, thanks guys. I will use the 3 blade fan with a longer belt to raise the fan up to hit on the core of the radiator. I will remove the thermostats and keep them safe.

Thanks guys,

 

[Ziggster]

A six bladed fan will definitely move more air. It will take more horsepower to do so, and will likely make more noise depending on its fan blade shape. The bigger, more powerful the engine, the more the reject heat will be. So, yes, in theory, you will need a "larger" cooling system to deal with the delta in reject heat. That typically would require more water flow, a larger heat exchanger, and more airflow. However, you would start with the one variable that was your limiting factor in the first place

 

[flatheadmurre]

First do you plan on running a fan shroud ?
That 3 blade fan is designed and works well without one...so it has an advantage right there compared to a truckfan.
The modern flexblade fans are designed to use with a shroud...most fans that have a straightcut edge are performing best running against a shroud.
Flow in the system isn´t dictating the fan...it´s more about Power/effiency of the engine that sets the need for cooling...and the the core itself how much suction you actually need to pull the air through it.
You can have a fan that pulls a lot of air but if it can´t handle a thick core it won´t work in the end.
So Flow of air and static pressure is the 2 things you need to calculate.

 

[mfirth]

I don't know what vehicle you're dealing with, but i have a friend with a 38 Ford car who runs no fan at all & has NO overheating issues. My 8ba with 400 Offy heads, Max 1 cam in a 52 Victoria has 180 stats & runs GR8 with a 3 blade....no over heating. My 2 cents, or, nonsense......

 

[3739ford]

Mfirth, this is all going into a 1939 Ford Pickup 1/2 ton. It has taken 2 years to get this far, and another 2 to 3 to get the body ready. I have to cut out some rust and weld in new panels. The welding I can do, but I have never worked with fiberglass/bondo going to broaden my horizons for sure.

Just trying to tap into experience here and see what works and what doesn't. Everything is easy to get to right now.

Thank you,

 

[marko39]

First do you plan on running a fan shroud ?
That 3 blade fan is designed and works well without one...so it has an advantage right there compared to a truckfan.
The modern flexblade fans are designed to use with a shroud...most fans that have a straightcut edge are performing best running against a shroud.
Flow in the system isn´t dictating the fan...it´s more about Power/effiency of the engine that sets the need for cooling...and the the core itself how much suction you actually need to pull the air through it.
You can have a fan that pulls a lot of air but if it can´t handle a thick core it won´t work in the end.
So Flow of air and static pressure is the 2 things you need to calculate.

You are correct about airflow and static pressure. Although fan cfm and total static pressure cannot be measured in this situation, fan air velocity could.What you want is the highest velocity of airflow through the inlet of radiator. This can be measured with a velometer.

 

[oldskool]

I had a 40 pu w/8ba w/6 blade fan very noisy in 1st and 2nd but ok in hi gear,ran ice cold even in traffic

 

[Ross F-1]

I am running a 3-blade fan with shroud in my 52 pickup, 4-row radiator, +.060 EAB. No overheating whatsoever in 100 degree weather, slow traffic or highway speed.

My biggest concern with fans is that they are all very old, and throwing a blade is getting more and more likely.

 

[PeterC]

The 6 blade fans sound like an airplane taking off. They also chew up your horsepower to make that noise. The 180 thermostats are good, and the shroud is by far the best thing you can do.

I run a 6 blade with fan close to the radiator cooling a high horse 284 cu flathead. works like a charm and quite honestly the noise level of the fan is not noticeable - yes I have mufflers.

 

[51 MERC-CT]

Adapted a 7 blade '70's vintage Ford flex fan. It's quiet and pumps a lot of air. So much so that I removed the shroud that was installed as it really did not need it.