After I lost a timing cover bolt (and my coolant) I removed the clutch fan, and installed a 6-blade fan.  Ever since, when accelerating above 3000 rpm, I have a whirring/turbine sound (like a jet engine spinning up).  Before I go to the trouble of removing the fan (to satisfy curiosity…could be also something related to the engine having been overheated), I’m wondering if anyone has had a similar issue (?).

6 VOLTS/POS. GRD. NW INDIANA

I have a 6 blade and never noticed the extra noise. My engine is rarely over 2500. 2300 70 mph with my gearing on the highway.
If you having a cooling problems install a 5+ inch 289/302 water pump pulley to speed up the pump at idle. I needed a shim kit to line up the belt and a shorter belt. Probably could go back to a 4 blade fan. To the nay-sayers my pump does not cavitate. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Great.  Now (assuming the noise is still there after I pull the fan), I have to figure out what could be causing the turbine whine..  Must be nice to never be in a hurry.

6 VOLTS/POS. GRD. NW INDIANA

I put a 6 blade all steel one on my car and have the same issue. I only hear it when I go to above 3000 rpm in first and second gear, in third OD on the hiway I don't turn enough rpm to here it.

Thanks Jim.  Saved me some trouble.  Weird though, as my steel 4-blade never made any such noise at high rpm.  5-blade alum. one I just removed also never turned fast since it’s clutch didn’t get hot enough.

6 VOLTS/POS. GRD. NW INDIANA

My '55 Tbird has 4.10 gears with a manual O/D transmission. I like to run through the gears, but I don't like the noise from the belt driven fan.  Sounds like a whirl wind to me.  This is how I fixed it. It never overheats even in heavy traffic.

Funny sidenote:  Since the fan’s ‘turbine’ whirl kicks in about when the torque curve peaks, you know when you hear it that it’s time to shift. (no longer need to watch the tachometer) 😁

6 VOLTS/POS. GRD. NW INDIANA