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IIRC the fan clutch is designed to freewheel above 4000 rpm so the question of the fan blades being over revved should not be an issue. Does anyone know differently?
I don't know, but I'd hope so, considering the harmonic balancer pulley is larger than the water pump pulley, resulting in the fan blade spinning faster than the engine rpm. I'd have to measure to do the math, but I can imagine it would be very easy to get a 289 to the right speed to cause the fan to surpass 4000 rpm.
 

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Discussion Starter #22
IIRC the fan clutch is designed to freewheel above 4000 rpm so the question of the fan blades being over revved should not be an issue. Does anyone know differently?
Don't know about the factory Ford clutch but for the Hayden clutch, per the Hayden website their standard duty clutches rotate the fan 60-70% of the water pump shaft speed when engaged, but still 20-30% when "dis-engaged". I guess it depends on the water pump pulley size vs. crank pulley size to figure out engine speed vs. water pump speed??? The Hayden 2710 clutch is what I went with and it's a standard duty.

https://www.haydenauto.com/en/products/fan-clutches/fan-clutch-types/thermal

In addition to the 2710 clutch, I went with the Derale 17117 6-blade fan. Doesn't look out of place, seems well balanced, no vibrations, and at idle the engine compartment is much quieter now. I did need a 1/2" spacer to get the fan a little closer to the radiator. With the spacer, the front of the clutch is 3/4" from the core and the fan blades are just about half-in, half-out of the shroud. Perfect.

Thanks to everyone for their knowledge, help and suggestions! Using the expertise on this forum has helped me avoid many expensive "trial and error" mistakes. Thank you!

Bill
 
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