Clutch Fan Questions?

[horseballz]

Hey All,
Some posts lead me to believe that a fan with a thermally operated clutch provides better air flow than a fixed clutch? Can I assume that this is because, at higher speeds the fixed fan actually impedes air flow? My current 5-blade, spring steel bladed OEM fan sits 2 inches from the radiator at the top and about 1-3/4 inches at the bottom and sits right at half of the fan into the OEM, 68/289/AC shroud. I've read that half way into the shroud is optimum, but also read that the fan should be 1 inch or less from the radiator. Which of these is more critical? In my parts pile I have a 7-blade clutch fan with a faulty clutch and before I spend for a new clutch, I need to know if it will give better flow than what I currently am using. It will give me the same distance to the radiator. I guess I should note that the 5-blade fan has a difference of almost 1/2 inch in the amount the blades are swept back from the most swept to the least. I mention this, as I have read that as these fans get older they lose some of their oitch and efficiency. I ask all this, because I'm currently reinstalling my A/C and want to absolutely maximize my cooling. Also, I assume that I can't run a clutch fan with a spacer to get it closer to the radiator?
Thanks,
Gene

 

[2+2GT]

Some posts lead me to believe that a fan with a thermally operated clutch provides better air flow than a fixed clutch? Can I assume that this is because, at higher speeds the fixed fan actually impedes air flow?
No. It's because the non-thermal operates, at reduced rpm, all the time, hot or cold. The thermal only operates when needed.

My current 5-blade, spring steel bladed OEM fan sits 2 inches from the radiator at the top and about 1-3/4 inches at the bottom and sits right at half of the fan into the OEM, 68/289/AC shroud. I've read that half way into the shroud is optimum, but also read that the fan should be 1 inch or less from the radiator. Which of these is more critical?
The 1" is true only when you have no fan shroud. With a shroud, centered in the opening is the rule. I have a car with the fan about a foot from the radiator, but it's centered in the shroud opening, works great.

In my parts pile I have a 7-blade clutch fan with a faulty clutch and before I spend for a new clutch, I need to know if it will give better flow than what I currently am using.
Your "spring" comment leads me to believe you have a flex fan. Pumps air all the time, even when you don't need it. Sounds like a Piper Cub when you accelerate. A 7-blade with a thermal clutch is superior in every way.

It will give me the same distance to the radiator. I guess I should note that the 5-blade fan has a difference of almost 1/2 inch in the amount the blades are swept back from the most swept to the least. I mention this, as I have read that as these fans get older they lose some of their oitch and efficiency. I ask all this, because I'm currently reinstalling my A/C and want to absolutely maximize my cooling. Also, I assume that I can't run a clutch fan with a spacer to get it closer to the radiator?
Refer to the above discussion of the shroud. Clutches come in various lengths to center properly.