Mechanical Fan Interchangeable?

[MikeyMan]

Are most small block mechanical fan & clutches interchangeable?

I've got 2 fan w/clutch setups, but don't know which was which

One is off an 84 Olds 307, and the other from my truck.
Truck is a 72 C/10 non A/C, but motor a late 70's 350 w/TH350 trans. Truck did not have a shroud when I got it, but I do have one I may or may not use.
I'm finally putting the truck back together after several years in pieces. Nothing special, just a stock daily driver.
So there's the two fans in my parts pile: One is a 6 blade that looks real similar to my 71. However, one of the blades is slightly bent and the fan seems to rub the shroud opening. The other is a 5 blade, and clears the shroud nicely. Both fan clutches are in good shape.

I'm going to use the 5 blade because it's in better shape and will clear the shroud if I decide to use it. I think this might have been the Olds 307 fan.

Is it OK to mix or swap small block mechanical fans?

[Stocker]

As long as it fits, it should work just fine. That said, some fans pull more air than others, and some clutch units work better in extreme conditions than others. The worst that can happen is it might not provide enough cooling pulling heavy loads and / or in hot weather. I would advise using the shroud since you have it....

[MikeyMan]

Thanks Stocker!

Kinda what I was thinking.

I've had a couple trucks that ran fine with no shroud, but no A/C of course.

I believe I will use the shroud. Especially for the safety factor. Born with 10 fingers, like to keep 'em.

[Andy4639]

Whatever you do don't use the fan with the bent blade. It will cause all kinds of trouble. I know from experience. Take the fan off the cluth and use it on the other one if need be. Just don't use that fan.
I took out 3 new NAPA water pumps before I figured out it was the blades of my fan.

[MikeyMan]

Thanks Andy!

I have heard a bent blade is bad news.
That fan was rubbing the shroud too.
I'm going with the 5 blade and shroud and will keep an eye on temps.

[LockDoc]

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The SB Chevy water pumps have 2 different bolt patterns where the fan hub bolts on. Some fan hubs have slots in them and some just have holes. The hub with the slots will fit both bolt patterns and the hub with the holes will only fit one. I don't know what dictates what pump has what bolt pattern though...

LockDoc

[benny70]

Hey mikey, can i ask how big the fan is, or should be? Im not sure if i need a 17, 18, 19, or 20 inch

[Stocker]

It might vary depending on how the truck is equipped & optioned.... my K20 with factory A/C has an 18" seven-blade clutch fan.

[Sammy]

Use the shroud on the SB to suck enough air this summer. You will regret not using one when it is 95 degrees again.

[benny70]

Thanks Stocker!