Stock fans: Is more blades better?

[dremu]

My 74 K5 has seven blade fans (350, gas) ... but my '84 has only five (military 6.2 diesel.) The 454's have five and six blades.

I didn't measure but I'm guessing they're interchangeable ... all other things being equal, i.e. engine RPM and fan clutch working, I would think that the big blocks would want/need more air, i.e. more blades?

I see LMC seels 5 and 6 ... but no 7. What's preferable?

-- A

 

[pauly383]

Depends on pitch , etc .

In home a/c motor applications , I replace 2 or 3 blade fans with 4 blades all the time at my store . 4 blades less agressive than the original 2 or 3 , equals the same with less power needed to turn it .

 

[dyeager535]

I would suspect that GM knew by the drivetrain combination how "much" of a fan the vehicle would need. The trucks used just about every fan combination under the sun: 3, 5, 6, 7 blades, clutch, no clutch, etc.

You are right, given the same accessories (AC, power steering, etc) the larger engine should need more cooling. But since there was also a large difference in radiators used, perhaps the larger radiator offset the need for a more efficient fan?

How about the clutches? Why are there different ones of those, when the engine temps were all the same? Probably tied into blade count as well somehow.

Some of it may have been noise related too. Depending on construction, GM could certainly have made the fans quieter or louder, and blade count probably influences that.