Correct position for mechanical (or flex or not) radiator fan

[70SSRS350]

I need some advice about mechanical radiator fans.

The mechanical fan in my '70 have about half blades inside and half blades outside the shroud. (Well, to be honest it's a bit more outside than inside..)

Anyway... Is it ok? I think yes, but I think it may be better if blades are about 100 % inside.... or not?

Being half outside/half inside, the fan is a bit far away from the radiator.
I noticed that electric fans are completely inside the shroud and very near to radiator.
I know that the engine moves, vibrates and rotates so mechanical fans needs much more room than electrical.
But now from radiator to first blade edge there is about 4,5 inch.

My fan is a simple, black painted steel mechanical fan but I think it's not stock beacuse there is an aluminium spacer (similar to those for flex fans) and there is no clucth.
I don't think it's stock GM.

 

[txwooley]

That is the reason for the shroud. As the fan blows air out of the shroud toward the engine, air flows through the radiator to replace the evacuating air. Halfway into the shroud opening is optimal for a mechanical fan. Too far in and you recirculate some of the air instead of evacuating it. Too far out and you pull air from the engine compartment. Both reduce efficiency.

 

[krabben1]

From what Ive seen,the small block fans are usually all the way inside the shroud,fully covered,while the Big blocks are half in,half out like you describe,as mine sits.
Either way,you want to be within(your fan,fan clutch)3/4"-1" of your radiator for best results.

 

[CorkyE]

Here's a picture of my '79 Z28, has original clutch fan and shroud, and it's bout 1/2 in/out.

 

[hhott71]

The mechanical fan in my '70 have about half blades inside and half blades outside the shroud. (Well, to be honest it's a bit more outside than inside..)

The correct stock position.

No Flex allowed.

 

[ZS10]

For functionality 1/2 in/out of the shroud.

The fist time you get bit, or drop a wrench on an exposed running fan, you reevaluate the 1/2 out. Make a habit of working on a running engine, and electric fans look very good.

 

[70SSRS350]

The correct stock position.
No Flex allowed.

What?
No flex fans at all or flex fan needs a different set-up?

Sorry for my basic questions, here in Italy is a bit difficult to obtain reliable answers about these things....
Most cars here (even historic ones) have transverse engine, so no mechanical fan.
The only cars I've seen here with mechanical fans similar to mine are old Mercedes and Bmw.

 

[Rockhound]

Flex fans are always spinning at engine rpm. They'll rob engine power. A clutch fan will free up some power as they will somewhat freewheel if the temperature isn't up as in driving down the highway.

 

[70SSRS350]

Flex fans are always spinning at engine rpm. They'll rob engine power. A clutch fan will free up some power as they will somewhat freewheel if the temperature isn't up as in driving down the highway.

Yes, I understand but my fan (black painted steel fan) now is already spinning all the time because there is no clutch.
As I wrote in my first post, now there is an aluminium spacer between fan and water pump.
This aluminium spacer looks similar to those for flex fans, but my fan doesn't flex at all. The fan itself is heavy steel and looks stock GM.

Maybe, in the past, the fan clutch broke and one of the previous owners replace the clutch with a solid spacer... maybe to save money or because the clutch was not available here in Europe (in pre-internet era...).

 

[fbody_mike]

Is it a 4 blade? That's how my 1970 C10 with a 307 was built. Aluminum spacer too.