8 BLADE FAN VS. 6 BLADE

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C

crash1964

Joined
Oct 8, 2025
Threads
7
Messages
23
Location
Cuero, Texas
Ok folks, obviously an 8 blade should produce more scfm than the 6 therefore, my question is, can anyone possibly quantify the approximate difference? If not or if it is an insignificant difference, I won't bother upgrading. It's just that I am in South Texas and plan to install a/c soon and would rather maximize airflow before overheating etc.
Heck maybe someone knows that the 6 blade is plenty in my area.
Thank you in advance for opinions and advice.
 
I have my metal 4 blade my 72 came with in 82. I put in a 160 degree thermostat - it always runs cool. Most times I run a curtain blocking 1/4 to 1/2 of the lower radiator. Once in the spring thaw out in the desert I was in low range low in mud to the hubs for about 20 miles - I had to stop twice; once to lower the curtain and the second time to remove the curtain completely or it wanted to run hot. I bought a new brass new 4 core brass radiator but never have put it in.

Pitch is important factor. Look at planes. 2,3,4 blades common 5,6 less so.
 
charliemeyer007 said:
I have my metal 4 blade my 72 came with in 82. I put in a 160 degree thermostat - it always runs cool. Most times I run a curtain blocking 1/4 to 1/2 of the lower radiator. Once in the spring thaw out in the desert I was in low range low in mud to the hubs for about 20 miles - I had to stop twice; once to lower the curtain and the second time to remove the curtain completely or it wanted to run hot. I bought a new brass new 4 core brass radiator but never have put it in.

Pitch is important factor. Look at planes. 2,3,4 blades common 5,6 less so.
Click to expand...
Thank you. Very good point.
I hadn't considered pitch, the fact I have a 3-row aluminum radiator, or the t-stat.
 
Or..... What about a 7 blade fan!? I've upgraded from 4 to 6 to 7 blade fan.... Check this one out. It's aggressive looking and it has some extra small fins on the actual fan blades. Pulls a lot of air.

Fannn_5000x.webp


This is an Fj60 radiator fan. Will work on an Fj40, and if you have an early 1973 or before, you will need a new water pump, fan clutch (get an fj80 one) , radiator shrowd, and push you radiator more forward (toward your headlights) so you can drop it in
.
I don't have actual scientific numbers to display for you. The only way I've tested was putting my hand in the engine compartment while it was running and feeling how much air I could feel beeing pulled around the engine. At the time, I had the 6 blade "upgrade' plastic fan (with fan spacer) and my father had this fan on his Fj40 . We both turned on the engines and compared the airflow difference and it was significant.

This Fj60 one wins, hands down and I've been running one since. I use it on highway speeds or low-and-slow 4x4 scinarios with zero issue. I live in a hot desert environment with summers reaching 105-110. I haven't tried an 8 blade fan though. Hope this helps you decide.
 
DesertFJ40 said:
Or..... What about a 7 blade fan!? I've upgraded from 4 to 6 to 7 blade fan.... Check this one out. It's aggressive looking and it has some extra small fins on the actual fan blades. Pulls a lot of air.

View attachment 4132376

This is an Fj60 radiator fan. Will work on an Fj40, and if you have an early 1973 or before, you will need a new water pump, fan clutch (get an fj80 one) , radiator shrowd, and push you radiator more forward (toward your headlights) so you can drop it it
.
I don't have actual scientific numbers to display for you. The only way I've tested was putting my hand in the engine compartment while it was running and feeling how much air I could feel beeing pulled around the engine. At the time, I had the 6 blade "upgrade' plastic fan (with fan spacer) and my father had this fan on his Fj40 . We both turned on the engines and compared the airflow difference and it was significant.

This Fj60 one wins, hands down. I haven't tried an 8 blade fan though. Hope this helps you decide.
Click to expand...

Do you by chance have the part number for that fan?
 
crash1964 said:
Thank you. Very good point.
I hadn't considered pitch, the fact I have a 3-row aluminum radiator, or the t-stat.
Click to expand...
DesertFJ40 said:
Or..... What about a 7 blade fan!? I've upgraded from 4 to 6 to 7 blade fan.... Check this one out. It's aggressive looking and it has some extra small fins on the actual fan blades. Pulls a lot of air.

View attachment 4132376

This is an Fj60 radiator fan. Will work on an Fj40, and if you have an early 1973 or before, you will need a new water pump, fan clutch (get an fj80 one) , radiator shrowd, and push you radiator more forward (toward your headlights) so you can drop it in
.
I don't have actual scientific numbers to display for you. The only way I've tested was putting my hand in the engine compartment while it was running and feeling how much air I could feel beeing pulled around the engine. At the time, I had the 6 blade "upgrade' plastic fan (with fan spacer) and my father had this fan on his Fj40 . We both turned on the engines and compared the airflow difference and it was significant.

This Fj60 one wins, hands down and I've been running one since. I use it on highway speeds or low-and-slow 4x4 scinarios with zero issue. I live in a hot desert environment with summers reaching 105-110. I haven't tried an 8 blade fan though. Hope this helps you decide.
Click to expand...
I like that aggressive style.
I have looked at 7 bladed fans, possibly this one.
I would need one for without the fan clutch as I cannot put a clutch on my 78 without h2o pmp replacement, and its newly restored so I'm out of funds. lol
 
I use a larger HJ fan for non clutch WP

16361-47010 is a 410mm 6 blade no clutch solid fan … it originally came on H engines

8 blades are loud … this one is louder than the thinner 6 blade … but not too bad imho
 
60090 stock 6 blade

1777590853308.gif


47010 H engines 6 blades
IMG_0019.webp
 
Designing and testing axial fans was my career for 15 years.

In very general terms increasing the number of blades does not equate to higher cfm. More blades are called for to overcome higher resistance pressure.

Much more important would be blade design. A stamped flat sheet metal blade is not going to compare to a modern plastic blade with a more engineered blade section and blade twist (steeper pitch at blade root to make up for slower blade speed).

And yes, pitch angle increase equals volume increase, right up until the wing stalls.
 
charliemeyer007 said:
I like my tractors simple, the less stuff to go wrong the better IMHO. Metal fan blade with no clutch
Click to expand...

usually yes for me as well.... but .... after metal one grenaded I'm sold on the plastic ones lol

technically a plastic one did as well... but it was not as bad :meh:
 
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