My '74 F-100 with a 302 does not have a fan clutch. As such I've got the equivalent of a huge propeller on the front of my engine that can't be doing my gas mileage any good when I'm traveling at highway speeds and don't really need the fan.

I was going to attempt to remedy this problem by installing a thermostatically controlled electric fan. I'm sure it would help, but I also found something else. I noticed that LMC truck lists a fan clutch for my year. This makes me wonder, is the fan clutch just a universal aftermarket piece, was it a factory option, or was it factory standard and some fool has removed it from my truck at some point?

The fan clutch is a lot cheaper than an electric fan, although it will still generate more drag than an electric one. The electric one though pulls like 13 amps and with only a 60 amp alternator, I'm not completely sure I wanna go that route either. There is something to be said for the simplicity of mechanical systems.

 

Sorry I can't help you with that problem as I have the same thing on my 79. Mine was a engine transplant to a 6/cy truck and I thought they just never put it on. I have one hanging in my shop I thought I might try to use next summer, to cold to work on it now. I did move the radiator three inches closer so I won't need a shroud, but that never helped on the fan noise . JIM

 

From what I can tell, there were three types of fans used on this generation. There was a solid rigid steel fan, a steel flex style fan, and there were the fan clutch style.

My '79 302 had the flex fan style, which is all steel unlike the aftermarket aluminum style. It howled all the time, which is annoying when its freezing weather. It measured 18". I went to a fan clutch style, but couldn't find an 18" in a truck at the yards, so I used one from an '85 Grand Marquis.

Hayden has an online catalog that lists the specs of every fan clutch they make. I believe I wound up with fan clutch #2710. That catalog can help you figure out what bolts up if you end up getting a fan off something else.

There are a bunch of threads about electric fans, as well as the alternator upgrades neccesary to power them. They don't sound too involved. I'd look into it, but my cooling system has stood up to the Mojave at its worst.

 

Mine has the flex/steel one and it howls. I'l be changing to a clutch fan,I have a couple,one is from a 460. I should have tried it when I was replacing the 460 with the 302.

 

I am mostly interested in fuel economy. Granted an overdrive transmission would help a ton, having that solid steel fan spinning all the time at highway speed has to be sapping some power and fuel economy. As far as alternator upgrades, I would really just have to wait and see. The factory alternator is a ~60amp unit. The fan I would like draws something like 13.2 amps. This might sound pretty bad but in reality, it probably won't be. The truck doesn't have all the modern bells and whistles of a new car, so the odds of exceeding the alternators output is actually pretty low.

Consider that the fan will only pull that 13 amps when it is running, and it will only be running when it is needed. If set up properly it will only need to run if I idle for quite a while. When moving, the airflow through the radiator should be sufficient.

Worst possible case for this truck would be to be stuck at in traffic on a hot day in the rain. Headlights and defroster blower motor would be the single biggest current draws other than the fan. Being stuck in traffic would have the alternator spinning at idle speeds and probably putting out a little bit less than optimal. Under these conditions it might overpower the alternator and begin to discharge the battery. Ultimately I won't know until I try it, but I'm willing to bet the truck really has such a low electrical demand that it would be just fine. Ultimately though, that's why I will wire everything properly so that my ammeter tells me the truth.

The other option, of course, is the clutch fan. It's certainly cheaper and doesn't present any electrical draw, but it won't be quite as good on fuel economy. I guess it boils down to how much money I have to throw at it. I put the electric fan on my Christmas wish list. If I get one, so be it. If not, I might look into the clutch option. Hence the reason I was curious. Was the clutch designed to work with my existing fan, was it different altogether, etc, etc.

 

Maybe you allready know this but the fan made for the clutch is different in the way it bolts to the clutch. A standard fan won't bolt too it. Since I allready have the fans, thats the way I will go if they will bolt on and clear everything. One is a chevy fan,if it fits right I will use it and leave the 460 one on the engine in case I need to use it in something else. The clutch fan cooled the 460 last summer too about 195 degrees ,no fan shroud and about 2 " back from the radiator. Im using the same radiator in front of the 302 so I should be ok. I thought about the electric fan just too save gas ,but It would take a long time to recover the cost of the fan in gas savings.Your situation might be different though.

 

No I did not know that the fan itself was any different. Then I'm into finding a fan and a clutch, which is more costly. Might not be as much as an electric fan, but the closer the price gets, the more attractive the electric fan gets.

I don't drive the truck a ton so it would take a good long time to make up any differences, but I would eventually like to build a supercharged 347 for it. I already have a 302 roller block sitting on my workbench. If I ever get to realize that dream, I figure I might want the electric fan.

 

100 amp swap fixes that problem about over powering your current system and discharing look into that. There are lots of swaps out there on this forum I would list a few myself but I feel like being only moderatly helpful =)

 

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It sounds like you have all ready got yourself convinced,get the electric one and good luck.

 

More or less. I figured that if the clutch had for some reason just been removed from my truck, I might see about picking one up and putting it back. Since it seems like that isn't the case and I would need a new fan and the clutch, it would be easier just to go electric.

If I go with an electric fan and start running into charging problems, I certainly will look into upgrading. That is exactly why I want my ammeter to work though, no sense in upgrading if I don't need to, the ammeter will tell me if I need to. I have looked at several aftermarket alternator solutions and most of them are either one wire and/or internal regulator style. I don't like the idea of the one wire's and since my truck is already wired for an external regulator, I would kinda like to keep it that way. Not sure why really, I guess I just don't like butchering up wiring when I don't have to, or having un-used pigtails just dangling around. So the question becomes, are there any upgrade alternators that will just hook straight up to the factory harness?

 

I can't help on the alt. upgrade ,but will be watching for the information too somebody will be along to help.

 

There are some darn pretty 140 and 200 amp ones out there, but I imagine all of them will be internally regulated. If I had just tons and tons of money I'd throw an electric water pump on it. I've had one on my Corvette for years and absolutely love it. Lots of benefits and no loss of reliability. Just gotta make sure you've got an alternator that will put out enough to handle all the goodies.

 

No - External - 1975 - F-100 - 5.0L/302 - FORD - Alternators and Generators - Ignitions & Electrical - SummitRacing.com

Badoow A bunch of externally regulated more than stock amperage altenators here some cheap some not so much one is even 200amp but its a pretty penny at $325

 

That 200 is probably so expensive because it's chrome. A 140 would probably be all I would ever need. That's what I have on my Corvette and it has more electrical goodies than this truck ever will. I like the powermaster name but they think highly of their stuff as well. But since it looks like there are no 140's and powermaster doesn't make anything above a 60 then it looks like a 100 or 200 it will be. Oh well, be some time down the road anyway.

Get me some pretty chrome brackets and a nice chrome power steering pump and a new intake and a new carb and a new everything else and it'll be good as new Ah if I only had money.

 

You and me both. Join the army they give out bonuses. Join the army the pay is great pfft. Have yet to see a good paycheck or my bonus.