I'm always out to gain a couple MPG from my Suburban. I'm also always out to gain a couple horsepower. When I can do both at the same time, I'm very happy!

Well, I'm considering the option of putting an electric fan in place of the factory mechanical fan on it. I've done this on my Jaguar with good results (significant horsepower and fuel economy improvement), but not on the truck. I have an electric fan out of a Lincoln Mk 8 that would be suitable (flows about 4000 or 4500 cfm). It has a low and a high fan speed, so I could just hook up the low speed to work when the AC kicks on, and the high to kick on at another time. So, here are my questions:

1) What sort of power/fuel economy gains have people seen when doing this?
2) Any problems with running hot on very hot days in traffic with the AC on?
3) Any problems with running hot while towing? I do sometimes tow smallish enclosed trailers or cars on unenclosed trailers.
4) Would it be feasible to just run the electric fans off of the auxiliary cooling fan switch in the block, or is that set to come on at some really high temperature like 235?

Any other info would be appreciated! Thanks! :)

Just a question....

Your electric fan came out of a 4.6 right?

You're putting it into your 95 with the 454?

This sounds like an awesome idea but do you think that fan that fed the 4.6 will shove enough air into the 7.4?

That is one potential question, Nick, and part of what I'm trying to find out. People use these fans in all kinds of high-horsepower applications. The factory engine made 280 hp (compared to my piddling 230), but it was also in a car not in a Suburban. The rating people give is about 4000-4500 CFM, which seems like it should be adequate, but I think my concern is more when climbing up a hill in Phoenix with a load.

If anyone who has experience with something like this can recommend another aftermarket setup or a factory setup that might be even easier, that would be great. But part of my thought with this Mk 8 fan is that I already have it, so it's cheap. :) Most of the setups I see online are in the $400-$500 range.

What about a stock GM electric fan out of a say, 05 or newer Silverado? How about a dual, high wattage electric fan set up out of an 06 or newer Police package Impala? Those move some air for sure...

I had buddies who did this. They always ran the fans to their own separate switch. They always wanted the ability to turn them on and off at will. Thats the way I'd personally do it.

I like having a separate switch to turn them on in addition, but the problem with that is that you can forget to turn them on. :) So, I end up opting for the thermostatic switch.

I suppose my question more goes towards the feasibility of using the fan I have. If I look at buying some other fan setups it's going to cost me a couple hundred bucks extra, whereas this fan I have is, well, in my garage.

One of my friends put a 2000 CFM aftermarket fan in his 80s GM truck with a 6.2 diesel and says he has no problems. He doesn't run the truck in as harsh of conditions as I do (he doesn't tow, for example), but if he makes due with only a 2000 cfm fan, a 4500 cfm fan would probably be adequate for me.

The linlon fan will work good. Maybe use 2 of them. My brothers K5 blazer has a Poniac 455 in i with 2 of the lincoln fans and it will cool itself down very easy.

How do the 2 fans fit? I'm not sure how I would fit 2 fans underhood.

Ya know, you sound like I do a lot of the time! :D I have toyed with this idea for my dually but I have stayed clear just because of the fear of heat. I do tow hard and that is usually all the truck is used for. (I can't afford fuel to drive it every day and I have a Honda and Subaru to put the miles on)

For the 454 I would recommend dual fans. If I were to do this, I would set it up exactly like my Cutlass. I have dual fans on that one as well.

I have a thermostatic switch in the intake that is set to come on at like 195* This goes into a relay and goes to the fan that is closest to the radiator inlit. Then I have the second fan on a thermo controlled unit that I set around 210*. This one goes into another relay. I have a dual post batter in my Cutlass. I built my own harness for the fans and they get bolted to the side terminal of the batter and the rest of the stock stuff goes to the posts on the top. In my truck, I would run the fans to the top post.

This setup has never had an issue keeping my 350 Cutlass cool. But it has an aluminum BE COOL radiator and never tows. I have only had the second fan kick on once and that was while testing. I disconnected the first fan so that I could get the engine hot enough to get to 210*. Both fans are set to be 100% power.

On your setup I would run off from the A/C line so that the fan comes on 50% power when the A/C is on. However, I think that it might be too low. Just the little I have played with A/C that stuff gets HOT.

No one has ever been able to tell me what a stock clutch fan can move for CFM. I know that when that clutch locks, it sounds like a freakin jet engine under the hood so I know they move some air. But my dual fans in my Cutlass can move some air also.

I've always wanted to do this on my dually, but I really do fear of going through all the work just to find out that I need to go back to the stock setup because it gets too hot.

Oh, one more thing, if you use one or two fans, make sure that you make a shroud for the fan(s). It will make them more efficient then if you just through them on the radiator. And make sure you let me know how it goes! :D

In my case the Suburban definitely doesn't get the same sort of hard towing use that you do, rockman. Most of its driving is solo (loaded with goodies). So, it wouldn't frequently present an issue. I suspect that the Lincoln fan would be good enough about 99% of the time, and with the auxiliary electric fan in front (any idea when that turns on?!) it probably would have enough cooling capacity, even when hot.

Maybe the thing to do would be install the Lincoln fan and, if I ever find it's not enough (and the auxiliary fan kicks on), install a second fan that runs with the auxiliary, and see if that works.

Part of the other question is time. I've got a trip coming up in early July down to Texas that I'm probably taking the Suburban on (doubt the Jag will be ready for such a trip at that point). Really, I would like to do this electric fan conversion before then. If I'm taking the thing on a couple thousand mile trip, then that will be when I'll see the biggest gain. But in the next couple of weeks I also have to finish the AC, change the exhaust manifold gasket, do something with the TBI, and get it painted. I may or may not also want to change out the interior carpeting. Probably going to wait on that.

The Mark VIII fan has a shroud built-in, so I would just use that.

We'll see what my time allows for, and yes I will take pics! :)

I would suggest you get it done as soon as you can. Then you can get some in town testing done. If you can't keep it cool in the city in stop and go traffic, I wouldn't even think about heading out on that long of a trip. It could spoil your plans.

I have no idea when that aux. fan kicks in since my 93 doesn't have one. But I do know that I had a pretty large (16 inch I believe) electric in the front of mine for a bit. I had to shove it over to the drivers side because I couldn't get a fan that big to fit in front of my large tranny cooler and that bracket for the hood. When I turned that on, it actually made things worse. And yes, it was pushing. It must've really disrupted the air flow bad because my temps would rise with it on!

So now I have this nice fan sitting there collecting dust. I have thought that it wouldn't take much money to buy relays, another fan, and start fabbing up my shroud.....but I just fear that "heat" word! :D

Of course I will also want updates on your trip if you do take the Burb! :)

Well, on the highway having the electric fan functioning or not wouldn't really make a difference because that's where there's enough excess air flow. You're right, it would be local traffic that I'd want to test in. Specifically, leave the AC on max on a really hot day in the sun and see what happens. When I was a Jag mechanic we always did this to test the cooling systems after installing a new radiator or something else that needed replacement. Since I only want to have to deal with one headache at a time, first I'll get the AC system sucked down and charged (which will be as soon as I get my vacuum pump/gauges in the mail... woohoo! New toy!) and then I'll think about it a bit further. I don't want to deal with wiring the fan up to work with the AC while at the same time charging the AC. I'd also want to run a couple of manual override switches, specifically one to turn off the AC fan when on the highway and it's unnecessary, and one to turn on the high fan setting, such as for towing up a hill.

I'll make sure to take pics and give details of the work and the trip. :) I'm going to make a big order from JC Whitney of stuff for the truck.

There is a company that makes a dual fan setup that is a direct fit for the full size gasser Chevys. I saw them in a 4wheel and off road magazine. I thought about getting those for my 8.1. I would use a thermo to turn them on, so I wouldn't forget.
I don't think one fan from a small engine will do it. You will need dual fans, like the ones on the 1/2 tonners.