My 79 F150 currently has a worn out pretty much non working clutch fan and no shroud and it gets warm at stop lights and pulling heavy loads.

I'm going to get a fan shroud for it and I want to ditch the clutch fan and get a Flexalite Flex Fan. This is on a 302, what size fan will work with the stock shroud and how close should I get the fan from the radiator? Also I need a standard rotation fan right? Not a reversed rotation. Thanks for any help.

I have been needing to do this for a long time and I have been hauling off scrap and have a little extra money now.

 

You ought to 3G upgrade your 79 and install one of those MarkVIII electric fans. There's a few threads floating around about it...As far as a flex fan...I wouldn't do it because they will create a lot of drag on your engine...wasted power.

 

Adding the shroud and a new fan clutch will certainly improve the cooling of the truck, without costing MPG. I dunno anyone that can really afford to lower their truck's MPG......

 

How is it going to cause alot of drag? When you get to a certain speed the blades on the flex fan start to straighten out and cause no drag.

The clutch fan on there now should cause more drag than a flex fan b.c the thing weighs a ton.

I'm not much on trusting electric fans, no matter how good they may be. Plus I need to fix this heating problem pretty much imediately b/c I am wearing the mud tires on my Bronco out using it to haul scrap.


Also the clutch fan that is on it isn't the correct size. A long time ago my dad put it on there and it was to big for the stock shroud so he threw the shroud away. So I have to get rid of what I got anyway to be able to put a shroud back on.

 

For maximum efficiency, a mechanical fan needs to be half-in/half-out of the shroud and the blades need to be at least one inch from the shroud opening.

If you want to run without a shroud, maximum efficiency is for the fan to be no less than one-inch from the radiator. However, that'll require a looooooong fan spacer.

Size and rotation? The biggest standard rotation fan that will fit without interference. Keep in mind the clearances due to engine vibration and torque-over.

Personally, I'd stick with a clutch fan (less parasitic drag) and maybe add a supplemental, thermostatically controlled electric pusher. My 65 Stang had an aluminim flex fan and it didn't appear as if the blades flattened out when rev'ed up. However, I do see nowadays that Flexalite offers fans with hard rubber trailing edges.

 

As for the blades flattening out at RPM. Yeah, they do, in most cases. However, they typically don't flatten much until well above the normal cruise RPM, therefore causing more drag on the engine.

 

The more I have thought about it I may go ahead and go back with a clutch fan. But what I am needing to know is what is the stock size clutch fan for a 79 302? As I said before along time ago dad put on a clutch fan that was to big for the shroud and thats why he threw it away to begin with.

I need to find a good stock shroud, a clutch fan that will fit the stock shroud, and buy a new clutch when I get the right fan.

My 73 F100 still has the factory 4 blade direct fan. I tried to get down in there to measure it blade to blade. Looked to be about 17 1/2?

The clutch fan that is on my 79 F150 right now I have no idea what dad got it off of. It is about a 19 1/2. It is completely wore out, you can tell it is barely turning even when the truck is hot, plus no shroud, plus no spacer so it is nowheres close to the rad. The truck has been ran like this over 15 years, lol.

 

It sounds like you have multiple issues to deal with.. the missing shroud, spacing, and the worn clutch itself.

But a clutch fan doesn't work off the engine temperature. Rather, it's the engine RPM and centripetal force applied to the fly weights and spring inside the clutch housing that engages at low RPM and freewheels at higher RPMs.

I'd start with getting or sizing the stock shroud since that's what will deermine the fan size and spacer that you will need.

 

I would stick with the clutch fan set up. It should kick in when it gets too warm and free wheel when you don't need it. Currently I don't have a fan shroud and haven't had one since 1988. Make sure your cooling system is in good condition, maybe upgrade to a slightly bigger radiator.

 

Clutch fans, when they work, are great. But are expensive to replace. I went thru some trial and error with them, and it was $$
There are some factory flex fans, I think in the larger 70's cars, been awhile. The flex's work great, mechanical, low cost and efficient for what you get.
Ive been using a factory flex, 5 blade, for a couple of years, works great, mind you my truck is mainly driven in the winter.
My next step is electric with proper relays, and thermostatic control. Not cheap but it will work good.
I personally hate the clutch fans, great massive blades attached to some cheesy device that will not transfer the power when needed. Proper function factory clutch fans usually are ok, but when they don't work, it sucks.

Yep, the shroud should be covering half the blade, with room for engine torque.
No shroud I think the front of the blade should be 3/4" away from the rad, and try to keep fingers on hands when engine is running.
Cheapest is old school non flex, factory flex, maybe aftermarket flex, then dedicated electric. I will not go back to clutch fans-my opinion.

 

Actually to tell the truth the clutch fan that is on it now works so poorly I wouldn't be scared to reach in and grab it with the engine running. You can put your hand behind it and feel pretty much no air moving doesn't matter if its hot or cold or if the engine is idling or reved up.

The radiator, hoses, and themostat are new. This isn't a new problem, the truck has always ran warm for over 20yrs and before I was even born.

Like I said before dad got rid of the shroud many years ago and the fan has no spacer on it, so it is a good 5 inches from the rad if not more.

Im just gonna start with getting the shroud and then Ill get a fan that fits the shroud.

Looks like for now Im still going to be taking loads to the scrap yard with the Bronco wearing down those expensive mud tires.

 

I PERSONALLY LIKE CLUTCH FAN ELIMINATORS AND A FACTORY FAN WITH AS MAY BLADES AS YOU CAN GET !