mech fan blade rpm limit?

Thanks, alot of good info, very true blind. I never thought of that, my wp pulley is larger than the crank. So at 4k the fan is spinning slower than the crank. Im still not sold on the clutch fan. How does it save hp? If it just dis engages at highway speed. If it stays engaged while the engine is warm and under full throttle then whats the point? I also would think that with it engaging and did engaging would put more strain under the water pump and belt

Just thinking here lol. I believe i have a original fan. Build quality should be pretty good right? Although it is old

Are the flex a lite fans a good option at all? They supposedly flatten out at higher rpm

The nylon one is rated to 8,000 rpm, any issue with the nylon warping with heat?