flex fans vs. clutch fans

Is it just a preference or is there some concrete evidence that a flex fan is better than a clutch fan.

I need to replace my current flex fan because the blades, in my opinion, are too narrow (1 1/4"). It is the next logical step in my quest to solve my heat issues.

What do ya'll think/know.

<font size=-1>[ This Message was edited by: swhite832 on 4/18/07 8:02am ]</font>

<font size=-1>[ This Message was edited by: swhite832 on 4/18/07 8:02am ]</font>

What kind of car?

The blades should be within 2" inches of the radiator. Must have atleast a 3 core radiator if you have a early model mustang, and an 8 cylinder.

You should have a fan shroud too.

If you do have a fan shround, the center of the fan should be halfway in the shroud and half way out of the shroud.

If you have any gaps between the shroud and the radiator, that should be blocked with some thin rubber, or other material.

It is a 69 with 302/328hp. motor. It has a shroud with a perm- a- cool flex fan w/1 1/4" blades. It cools fine while driving. It heats up while sitting. We haven't even hit average summer temps yet. I need more pull or more core or both. The set up now is not working. It is about 3" from the radiator. The fan is approx. 1/3 in 2/3 out. It has a two inch spacer. I could replace the spacer with a 2.5" but I think the blade surface area is inadequate.

The radiator is good. It cools while moving and I checked it with a temp gun.

I will upgrade to a 24" but not until next summer. So the plan is to replace the fan w/something more substantial. So which way to go. Preferrably something i can use with the 24" as well.

<font size=-1>[ This Message was edited by: swhite832 on 4/18/07 10:09pm ]</font>

The 69's have a good cooling system. Prior to 68, they did not.

You have a good fan position ( centered) and not a lot of HP.

Should be cooling just fine. Maybe your fan, or maybe your radiator, if it is old, and if it is 2 core... chances are thats your issue.

You are running a thermostat...right?? Running a thermostat keeps it cooler, then without. A long story

At Idle, feel the front of the radiator, and you should feel cold air going through your fingers at all corners and the center of the radiator. If so, it's not your fan.

Yes...I have tried both, 160 and 180. The 160 stays open all the time. The jury is still out on the 180. But it did open and reduce the temp. while sitting in front of the parts store(heat gun). The radiator has relatively good temps throughout via heat gun(no blockages).
The fan pulls air...,IMO, not enough(trying to confirm before I spend).
If it is not the fan...why does it cool off moving down the road?

I wish the stock guage had actual numbers.

<font size=-1>[ This Message was edited by: swhite832 on 4/18/07 10:57pm ]</font>

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
On 2007-04-17 17:00, swhite832 wrote:
Is it just a preference or is there some concrete evidence that a flex fan is better than a clutch fan.

<font size=-1>[ This Message was edited by: swhite832 on 4/18/07 8:02am ]</font>
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>
I don't know where you got the idea the flex fan was better?..I prefer to run a clutch fan .It's free hp..However I think you are talking more about the style of the blades of the fan rather than how it is driven..Have you tried a stock type fan?..They move tons of air but because of that they are noisy and suck a lot of power.That is why they are usually removed but they do cool well..
[addsig]

I have to replace my current flex fan because, IMO, the blades are too narrow. My choices are; replace with a flex fan with bigger blades or a clutch fan...with bigger blades. I have no clue which is better or why. It seems it is personal opinion at this point.
Based on the info graciously given by those who responded and others...I think I will go with a clutch fan.
My reasoning is it appears a clutch fan and flex fan basically do the same thing two different ways, that is, pull a given amount of air throughout all rpms. That being the case I prefer not work with spinning razor blades.
Next year, when I add a/c, I am going to upgrade to a 24" radiator and shroud. I will be able to utilize the clutch fan I buy now. When I add the a/c coil up front I will add, in addition, some electric pushers and have the best of both worlds. Lost hp, if any, is not an issue. This particular car has more than it needs.
Thankyou everyone for the input...if it doesn't work, of course i'll let you know.
sTw

what we run on the late model is a 4 blade inline 6 cyl gm blade, It is fixed design, set at 15/16 of an inch from the core. The car runs 180 after a 100 lap feature with NO shroud at all . We have done many tests with many fans, blade types, number of blades, distance, and shrouds. The high pitch 4 blade is the best, and with all blades except the flex a junks, 15/16ths was the magic number for spacing.
[addsig]

I have a 65 Mustang that Has a 4 core and a clutch fan. It cools so well I have to actually put some rags over the front, held on by the suction of the fan, to get it up to 180 at idle.

Measures 5/8"-15/16" away from radiator. Some of the blades on my fan are pitched differently. It is a 7 blade clutch fan.
[addsig]