6 blade fan

[mcgarrett]

Originally Posted by BRENT in 10-uh-C

To answer your question likely needs to know what conditions, or how you are driving your car.

Look at the frontal area of a Model-A radiator. Likely if you are driving at a speed of 20MPH or greater, the air is going to be forced thru the radiator at a greater rate than what a fan is going to pull it thru. The goal is that the radiator tubes needs to dissipate the heat into the flowing air.

The reason why a 4-blade fan was introduced was for the AA trucks that were generating excessive heat from hard pulling yet were driving at slow speeds (-think pulling a steep grade in low gear). In that case, more blades helped pull more air thru the radiator for cooling. The issue with too many blades is it can build a wall of air where the rushing wind at cruising speeds is faster than what the flatter fan blades can pull. At that point, you are impeding the cooling abilities of the radiator.

Brent,
The thought did occur to me about what you said in your last paragraph referring to multiple blades actually impeding effective airflow at some point. I'm not sure that I'm having an air flow problem or a heat transfer problem but want to be sure that the fan I'm using is doing the best job. With the heat wave we had here in Texas this past summer, my REXACO temp gauge climbed into the "Danger" zone while cruising at an indicated 50 mph but never boiled over. That made me very nervous. I do have the engine pans installed. Having to idle at traffic lights doesn't give me much confidence either. My radiator doesn't appear to have any problems, but with air temps this past summer at 108 degrees + I would like to cover all the bases. I think I'm going to get a fan shroud and see if that makes any difference.