6 blade fan

[BRENT in 10-uh-C]

Originally Posted by mcgarrett

I'm currently running a 4 blade steel fan like the ones used on the Model B vehicles. It seems to pull enough air on most days except the really hot days we have here in Texas. Does the plastic 6 blade fan sold by the parts dealers offer any better cooling or am I better off keeping the 4 blade unit?

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.