Was wondering if anybody knows off hand the size of a stock 4 blade fan on a 73 F100 with 302 so I don't have to pull mine off to measure. I think I'm going to change over to a flex fan. No heat problems but I figured the flex fan will pull more air at slow speeds and the reduced weight may give a small increase in power and milage. Been looking at the Flex-A-Lite fans. Thanks.

 

Fan blade assy.
Fits 73-77 F100-150 w/ 302 & std cooling or extra cooling
C9OZ-8600-A Marked C8SE-A

17 1/2" Diameter

 

What kind of fan do you have now? Clutch type fan?

Flex fans by design flex flat and do not pull as much air at faster engine RPMs as the solid fan will. This can be detrimental if you are pulling a long hill at high RPMs at slow speeds. Like pulling a trailer. The fan blades flex flatter the higher the RPMs untill it's cooling effectiveness is all but lost.

There are two different types of clutch fan. Centrifugal, and Thermostatic type (the one with a spring).

A Centrifugal Clutch Fan (working properly) will pull about the same amount of air at idle as it will full throttle. This is because the fan does not flex flat and turns about the same RPMs at idle as it does at full throttle. These type of clutch fans always slip a little. Why they cool about the same at Idle as they do at full throttle. These do not have the shortcomings of the flex fan. Their cooling effectiveness is not affected by engine speed as much.

A Thermostatic Clutch Fan, fully slips when the engine is cool, and only engages the fan when temps necessitate it. The hotter the temps the more the clutch engages untill it's full on. These are the best types of fans for cooling, as the blades of the fan does not flex flat, and when temps warrant turn as fast as the engine RPMs. These cool the best in situations of pulling a long hill at slow speeds but high engine RPMs. These are also the best for fuel economy as they are not taking engine power to turn unless needed for cooling.

If you have a clutch fan, and it's working and cooling fine, I would recommend staying with it. It will cool better and save you more MPGs than the flex fan will.

 

No it has the factory 4 blade direct fan with standard cooling rad. Its a F100 shortwheel base and I don't have a aftermarket hitch on it...it won't be doing any pulling. I do that with the F150 and Bronco. I keep it tuned up good and get good millage but I know with a different fan I could get a little more out of it.

The F150 and Bronco have a clutch fan but the fan on them is much bigger. Is there a clutch fan that will fit my current shroud? A new fan and the clutch to go with it will be expensive I'm sure I'll have to wait if I go that route.

 

Yes, there are 17-18" Fan blades and Clutches out there.

You can get the new clutch, but for the blade you will have to peruse the wrecking yard. A Solid Fan Blade from a 80's model should work if it's the right circumfrence in the fan. Just check over the blade carefully.

 

I have basically the same truck but mine is a 74' and has a 4spd. I have a had a Flex A Lite fan on it for many years already. Pulled a 3k boat with it a couple times also. The fan is mounted direct with no clutch.(spins all the time) Never had any issues even at sustained high rpm on the highway at 65-70mph in the summer. I don't remember the size or the rotation direction I bought as it has been over 10 years since I put it on. This is close to what I have. Flex-a-lite 1318 - Flex-a-lite Wide Blade Flex Fans - Overview - SummitRacing.com

Summit lists this a replacement fan for the clutch setup on our trucks.
Flex-a-lite 5718 - Flex-a-lite Standard Rotation Clutch Fans - Overview - SummitRacing.com