There has been a lot of discussion about which is the best fan to keep that Model-A temperature the coolest. Is the original 2-blade metal fan, the later 4-blade metal fan, or the aftermarket 6-blade plastic fan the best?

For this test a sophisticated instrument was used to measure the air speed in MPH (Miles Per Hour) at three different engine RPM’s (Revolutions Per Minute).  The results are not scientific but do give a good indication of which fan produces the most airflow.  The tests were performed on a stationary vehicle.  The following tests indicated the fan air flow MPH speeds with engine speeds of 500 RPM, 1,000 RPM, and 1,500 RPM.  The measurements were taken at the front right corner of the engine block.
 

Engine @ 500 RPM Engine     @ 1,000 RPM  Engine         @ 1,500 RPM
       (12 mph ground speed) (25 mph ground speed) (37 mph ground speed)
 Fan         Air Flow                           Air Flow                            Air Flow
 2-blade    7 mph                            18 mph                             25 mph
 4-blade   11 mph                           24 mph                             32 mph
 6-blade    8 mph                            22 mph                             34 mph

 The above Air Flow test results indicate:
1) The 2-bladed fan produces less air flow than either the 4-bladed or 6-bladed fan.
2) The 4-bladed fan produces the most air flow up to 1,000 rpm.            
3) The 6-bladed fan produces the most air flow at 1,500 rpm and higher.
            Summary:  The 2-blade fan should be adequate if the cooling system is up to par.  If not, more fan blades might be needed.  A cars higher speed will increase airflow through the radiator, but also increase engine heat.  Remember, a good clean radiator, correct coolant, and a tight fan belt are essential to good Model-A cooling.

This article was authored by Marvin Melage with data provided by the Model A Times Magazine.