240 cooling fan

[Blairsville Ed]

1968 F100. 240, 4 on the tree, 3.70

I just finished the ac system and it works well, however, yesterday I had the truck idling with the ac on for about 5 minutes and the temp gauge went up quite a bit. I have the original 17 inch steel fan with an add on clutch. The radiator is new although it’s larger than the original and there is NO shroud.
The clutch assembly moves the fan back from the radiator more than it was originally without the clutch.
A shroud would help, but.....
I wondering if a simple fix would be a molded 18 inch nylon fan without the clutch and get a spacer that moves it close to the radiator.
Also, how close to the radiator should the fan be.

[Max_Effort]

A shroud is a top priority!

The flex-A-Lite nylon fans move a lot of air, but the air isn't necessarily goin to be pulled through the cooling bundle, it can just be recirculating air, and pulling from the sides. The shroud makes the fan more effective and directs the airflow.

If you have a long shroud, position the fan flush with the shroud opening.

Short shroud, one inch from
The radiator.

No shroud, one inch from the radiator.

[THE FRENCHTOWN FLYER]

A shroud is a top priority!

The flex-A-Lite nylon fans move a lot of air, but the air isn't necessarily goin to be pulled through the cooling bundle, it can just be recirculating air, and pulling from the sides. The shroud makes the fan more effective and directs the airflow.

If you have a long shroud, position the fan flush with the shroud opening.

Short shroud, one inch from
The radiator.

No shroud, one inch from the radiator.

X2

Plus, a later nylon multi-bladed fan will significantly increase parasitic drag on the engine - enough to affect mileage.

[Jesse73]

I just ordered this "universal" fan shroud from summit, they also sell different size configurations to match your radiator:

https://www.summitracing.com/parts/sum-380482-sh/

Haven't received it yet but it should work with my clutch fan and radiator combo according to the tape measure. I can report back once I have it if you like.

-Jesse

[guhfluh]

FWIW, it will not stay cool without a shroud and with A/C. Been there, even with oversized V8 radiator.

Make sure the clutch is operational. It should be locked up solid when hot.

[Blairsville Ed]

I went with a 6 blade nylon fan, mounted 7/8 inch from the radiator. Over heating issue cured.
In retrospect, I caused my overheating problem by adding a clutch unit to the existing steel fan without adding a shroud. The clutch moves the fan blade away from the radiator which necessitates using a shroud.
I still may add a shroud sometime later but for now there’s no overheating and the ac works well.

I have noticed a bit more power climbing hills since the fan swap. Lighter fan maybe ? I did clean and regapped the points. The dwell was a bit long at 42 degree. It’s now at 37 degrees. Maybe that is what added some power.

[THE FRENCHTOWN FLYER]

I have noticed a bit more power climbing hills since the fan swap. Lighter fan maybe ? I did clean and regapped the points. The dwell was a bit long at 42 degree. It’s now at 37 degrees. Maybe that is what added some power.

yup

[sdiesel]

a taurus fan with volvo and bmw, sensors is a very successful combination. If you like Electric fans, which I do. the Lincoln mk 4 fans i'm told are even quieter and smoother.

I have it on my list to look into the electric fans on the newer dodge diesels. Now that , I imagine, would pull some air.