1940 6 blade fan
 

On the 6 blade fan on my 40 3 alternating blades are 6.5 inches long and 3 are 5.5 inches long. Anybody know why?

Re: 1940 6 blade fan
 

Reduce Noise? Provides easier access to work on front of engine?

Re: 1940 6 blade fan
 

Weren't most factory fans 4 bladed?

Re: 1940 6 blade fan
 

Every 39 deluxe-40 V8 fan I have seen had 6 blades.

Re: 1940 6 blade fan
 

Good to know...thanks

Re: 1940 6 blade fan
 

Yeah, that's a stock fan for a '40 Deluxe. Mine has the same thing...

Re: 1940 6 blade fan
 

Could be something like the " propeller wash " effect.
Anybody out there with an aviation background.

Re: 1940 6 blade fan
 

Probably more for sound reduction. The vortex from the leading blade tip will cause a pop when the next passes through it if they're the same size.

Lonnie

Re: 1940 6 blade fan
 

Also 1941 and 40-41 pickups with V8

Re: 1940 6 blade fan
 

Again, good to know. Thanks guys!

Re: 1940 6 blade fan
 

Advice for all fixers of crank mounted fan vehicles (39 - 41):

Before installing your fan, do a quick check by laying the fan face down on a flat table and see if all of the leading edges are touching the table. Then set it on the hub and check the that all of the trailing edges are the same height all across the length of all of the blades. Same thing for all of the leading edges. I installed a NOS six blade on my '41 without checking, and picked up a small but annoying vibration. Felt like the engine rotating assembly was out of balance. Drove the car without the fan and the vibration was gone. Adjusted the blades to level them out and all is smooth. The tip of one blade was about 1/2" low; another 1/4".

I put a crow bar in the center for leverage and was able to bend the blades up or down by hand, a little at a time.

Those fan blades bend easier than you might think. I will never again turn over the engine by pulling on the fan blades.

Re: 1940 6 blade fan
 

Likely set up that way so the fan doesn't get harmonic vibrations. With the blades spread evenly and the same length there is the possibility to get vibrations that get bigger and bigger that could break off the blades. If you look at the blades of a late model car they can be even more un-even to prevent the destructive vibrations. The analogy is pushing a kid on a swing. If you push at just the right time the kid goes higher and higher.