Upgrade mechanical fan vs installing electric fan

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Elwood blues

Elwood blues

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Doing and engine rebuild on a 5.7 hemi and then swapping into my 71 scamp. Will be replacing the water pump and fan clutch. Looking at either upgrading to a better mechanical fan or switching over to an electric fan. I figured mechanical upgrade would be easier, but electrical fan seems like it would have more of a hp upgrade. I am also unsure if I switch to electric if i would still have a clutch or if it would just be a pulley on the waterpump.
 
Well, there is very little HP gain by going to an electric set up but sometimes it just helps solve issues with swaps.

An electrical fan would be moved off of the water pump and the water pump is ether a stand along electrical unit or driven via a belt of a motor.
 
Tune into “EngineMasters” @ Motortrend.com for the fan shoot out and the “accessories drain” episodes.
 
When I switched to electric fans on my custom pickup I could definitely feel more power. It cleans up the engine and gives more room. I like the thermostatic control. Go for it!
 
I much prefer electric fans, for several reasons. One, they do a better job of cooling when the car is idling in traffic, because their speed is not dependent on engine RPM. Two, electric fans can be activated with the engine off to reduce heat soak. Plus, they generally provide more clearance in front of the engine, and allow a thicker radiator. Yes, there is a small loss in mechanical parasitic drag, but it's somewhat taken up by the additional load on the alternator.
If you go electric, you do not need a fan clutch, just a pulley.
 
In my own experience having both over the years, and currently electric I feel that the electrics are nice, but sometimes the reliability and capability to move enough air in hot weather makes the mechanical fans a better choice.
Nothing beats a good clutched fan in a shroud for cooling capability while minimizing power loss.
An electric can be added for intermittent use when needed.
 
I agree with RichB. I have done the swap before and Gary does have a good point. I can’t lie about that.
A lot of what your doing is dependent on what is easiest and what you need or can’t have as in the case of my BB Duster, I ran out of room with a thicker radiator.
 
If I do switch to electric would I need an electric water pump or would it be a mechanical water pump with just a pulley?
 
Yea, you can do just an electric fan. If you want. Just remove the mechanical fan. Or leave it. Run both? I don’t know your cooling needs and ability of what’s there.
 
Mechanical fans are more efficient at cooling than electric fans...
 
For a streeter, I'm with TB
The mechanical fan really only has to work below 30/35 mph; after that ram-air eases the load, and eventually takes over. So then,during ram-air cooling, and with a thermostatic clutch,the fan goes along for a free ride. Set your coolant thermostat up to maintain a minimum operating temperature, and the fan to to set the maximum, and give the carb fresh cold air, and your troubles will be over. Set it and forget it.
Because the thermostatic clutch does such a great job, I stuck an all-steel, 7-blade, high-attack, fan on the Milodon hi-flow pump, and that was about 2002.
So ok, it costs me a little power below 35 mph, so what; this is like 4100rpm in first and there is probably 150/200hp I can't use anyway cuz it just spins the tires. When I hit 60mph and stick it into second gear, she is well into ram-air,so the fan while freewheeling is being driven by ram-air and viscous coupling, doing nothing.
Driving in traffic I never feel the T-clutch cycling. But on occasion I hear it. But then, my engine is set up to maintain a minimum coolant temp of 205
 
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I'll always go with belt driven mechanical fans over electric when fitment is not an issue.
simplicity.

electric fans are powered by the battery.
takes hp to keep the battery charged, doesnt it?

so they BOTH use HP to provide cooling.
 
Maybe because I live in Phoenix I'm more sensitive to the engine heat that builds up in low speed stop and go traffic. I have a 14 mile commute to work every day, and during that trip, it's not unusual to spend 15 minutes sitting at red lights, or in heavy traffic going under 15 mph. In those situations, I have had much better engine cooling with electric fans.
I had a car with a mechanical fan, thermostatic clutch, and well fitting fan shroud. Sitting at a red light when it's 100 degrees outside with the engine idling, the coolant would reach 205 to 210 degrees. I replaced the mechanical fan and shroud with a pair of 14" electric fans and a different shroud, and now the coolant temp never gets higher than 195, even when it's 110 degrees out, and I have the A/C on.
If you don't have to deal with my sort of high ambient temps, or you don't ever sit idling in traffic at 100+ degrees, I agree a mechanical fan will work great.
 
Good mention Gary. It is a rare day in New York that we see 100*. It happens for a day or two at worst. For the most part, the factory set up is best. The move to an electrical fan set up should always be done with the best components.
 
Can any of you provide mechanical fan, shroud and clutch recommendations for a 512 stroke BB. in a 73 scamp. Radiator recommendation also welcomed.
 
Garry in AZ said:
I much prefer electric fans, for several reasons. One, they do a better job of cooling when the car is idling in traffic, because their speed is not dependent on engine RPM. Two, electric fans can be activated with the engine off to reduce heat soak. Plus, they generally provide more clearance in front of the engine, and allow a thicker radiator. Yes, there is a small loss in mechanical parasitic drag, but it's somewhat taken up by the additional load on the alternator.
If you go electric, you do not need a fan clutch, just a pulley.
Click to expand...

The power loss of a fan goes up exponentially with speed, i.g. the reason for the fan clutch. Its very significant _ probably double digit horsepower to be gained with electric fans.
 
RichB said:
The power loss of a fan goes up exponentially with speed, i.g. the reason for the fan clutch. Its very significant _ probably double digit horsepower to be gained with electric fans.
Click to expand...
A fixed fan does NOT go up exponentially but does increase more over a clutch fan.
 
Granted it was a daily driver but my electric fan died for the second time and 2 warped heads and blown head gaskets. If the car wasnt built with one id ditch my electric, Texas gets hot in the summer.
 
rumblefish360 said:
A fixed fan does NOT go up exponentially but does increase more over a clutch fan.
Click to expand...
Let me give you an example from fan charts. I f you have a fan that takes 5 hp @ 848 rpm to produce 2.5 in. static pressure, at 1383 rpm, a 63 % speed increase, it will take 21.7 hp , or a 334% increase in power to produce the same 2.5 in. static pressure. That, my friend, is an exponential increase in power.
 
And that it would be but I haven’t seen it myself.
Could you expand on the 2.5 inch of static pressure and where it is measured? I’m trying to see how this works on a car. I’m not getting a clear picture of this.
But those numbers would certainly fit the bill!

TIA Rich
 
The horsepower is of course the loss to the car engine to drive a fixed pulley belt driven fan.The power loss to the engine goes up by the cube of the engine and fan speed. All of the air moved at a high fan rpm is not needed to cool the engine. A fan clutch allows the fan to run at lower speeds and save a lot of engine horsepower. Electric fans run at constant speed, only when needed, and save even more engine power. Maybe we can find some actual comparison numbers for a car at an electric fan website.
Static pressure is the resistance to the airflow caused by pipes, baffles,etc. Measured in inches of water. It is usually used as a constant in fan charts.
 
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Ok gotcha! That measurement I haven’t found anywhere prior. For a fan comparison, if you have motortrend on demand as so to tune into enginemasters for there fan shoot out, they make a few comparisons on fans in one episode and in another they have a comparison of engine power drainages with electric, mechanical water pumps and then a alternator. I forget what I just seen the other day. This is where I say the power loses aren’t exponential. But I can see where your coming from. The constant pressure of *** number needed to be sustained at increasing rpm ‘s would need what you say but doesn’t hold to the dyno testing performed on video.

At least the way I see it. In the video. Perhaps I should revisit the video. It maybe there and I didn’t realize it in the way you presented it. (It’s probably there.)

It was a good video. Check it out.

Thanks Rich!
 
You might do like my 1985 M-B diesel. It has a clutch fan, plus a pusher electric fan. The electric only turns on from AC refrigerant temperature at the filter/drier. I put one on my 1965 Dart. My 1964 Valiant already had a M-B pusher fan when bought, with no mechanical fan. It isn't sufficient to cool the radiator itself. Even worse, some gomer wired it directly to the ignition switch (no relay), plus ran the wires thru bare holes in the firewall w/ sharp edges (no grommets). I am keeping it to help the AC.
 
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