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Discussion Starter #1 (Edited)
I converted my 67 Mustang to an electric fan nearly a decade ago and have never looked back. Electric fans just make so much more sense then mechanical, belt-driven. They are more efficient, better cooling, safer, lighter and the list of advantages goes on and on. Though I am surprised people still choose to run mechanical fans, I can understand that selecting the proper electric fan can be daunting. However, it shouldn't be, as I will explain and show in this article.

The criteria I use when looking for an electric fan is this: buy the highest CFM fan that physically fits your available space. (Obviously you must consider your own budget constraints.) Let's address physical space first, because there will surely be some contention regarding my CFM advice. Physical space simply refers to the area across your radiator, where the fan will mount, and the distance to any component off the front of the motor that might interefere with the fan. Generally, it is the waterpump or crank pulley which limits how thick of a fan can fit in the space. Most electric fan manufacturers list the dimensions of their fans. The key measurements to look for are the diameter and the thickness.

More on Fan Thickness
Be aware that most companies provide a fan thickness dimension measured at the thickest part - which inevitably is the fan motor in the center of the fan assembly. I have found this to be problematic, because many fans, like the Summit one pictured below, are convex shaped and it is the thickness of the grill area that causes intereference with pullies. On my '67 I usually run a serpentine supercharger pulley on the crank, but you'll notice in the picture below I had to remove it due to the thickness of the Summit fan in that area. In fact, I tried 14" and 16" fans from Derale, Flex-a-Lite, and Imperial to no avail. They all listed fan motor thicknesses between 3.5" and 4.5", but neglected to indicate thickness of the actuall fan and grill area. All of these fans were well over 2.5" thick at some parts of the grill, making a very tight or impossible fit.


Summit 16" fan shown above. Though the thickness at the motor is 3.5", the grill area is so thick I had to remove the blower pulley due to interference.

In my search for a super-thin fan that offered significant (1800cfm + flow) I came across a brand I had never hear of, Maradyne High Performance Fans. They offer a number of fan diameters, including the M162 and M166 series 16" fans. The M162 is actually used by many NASCAR teams. It has a 3.175" thick motor and pulls 2170cfm (17.7amps). The M166 has a slightly smaller motor at 2.87" and pulls 1810cfm (12.3amps). Both fans however are just a touch over 1" thick in the grill/blade area! I went with the M166 because I wanted the thinnest motor I could find, and also wanted low amp-draw to avoid having to use a relay.


I went with the Maradyne M166. The motor is only 2.75" thick, and the rest of the grill area is a little over 1" thick.


The M166K and M162K are the thinnest electric fans I have ever come across, and I have tried just about every brand (Derale, Flex-A-Lite, Imperial, and Summit.)

CFM Explained

Those of you who are familiar with cylinder head flow testing know that CFM numbers can be decieving. In fact, without a static pressure value and a battery voltage value, fan CFM numbers are rather meaningless. Most fan companies advertise a CFM number at zero-static pressure. In other words, this is how well the fan will flow with no resistance from radiator fins or ambient air flow. Keep in mind however, when the fan is actually mounted you would expect to see some value less than the advertised cfm. Maradyne does a nice job on their website of showing cfm at various static pressures.



The second factor is the voltage applied to the fan motor. Clearly the more voltage applied the faster that motor will turn, to a limit. Therefore it is wise to seek out the voltage at which the advertised cfm is being calculated. Maradyne shows that they apply a constant 13.5V for their ratings. This would be a typical 12V battery voltage while being charged by the alternator.

Earlier I said to go with the highest CFM you can for that fan size. In my opinion you can't go wrong with more flow. Of course, this is assuming that you are comparing apples to apples with good data per the aforementioned understanding of voltage and pressure. To simply take a company's advertised "2400cfm" rating without considering these other factors is likely to leave you with a fan that underperforms.

Finally, be sure to consider the amp draw. If the draw is over 15amps you really should use a relay to ensure full delivery, and prevent amp drain from other electric components in the vehicle. Below 15amps and you are likely to be fine running off the battery, but do use a 20amp inline fuse and the proper gauge wiring.


This image shows just how decieving fan thickness ratings can be. The Summit fan (right) has a taper to it that unfortunately increases the chance of intereference with pullies.



Note the integral reinforcement rings and balancing weights. Many electric fan blades flatten out as rpm increases, the rings prevent this to ensure fan efficiency is maintained.


The Maradyne fan can be a puller (preferred) or a pusher (mounted in front of the radiator), by simply flipping the fan blade per the instructions.


Maradyne includes some nice rubber spacers to mount the fan at the proper distance off the radiator. Surprising most electric fans on the market mount right up against the fins and have too little distance between the blades and the radiator - thereby losing efficiency.


I was able to get the 16" Maradyne easily mounted in the stock 1967 Mustang fan shroud. I have found this actually provides even better cooling by directing all air is pulled from front of the car and through the radiator. Note the blower pulley is back on and there is significant room to the fan. The motor edge is still 3/8" away from the pulley edge.


Conclusion
Hopefully this little tech piece has helped some of you who are considering an electric fan upgrade or conversion. It really is worth it, and as you can see in the short video below, the Maradyne fan moves some significant air! I see no problems in cooling my 500HP supercharged 331.
The only problem might be finding Maradyne fans. They aren't sold at the big catalog places, but if you Google it you will find plenty of small speed shops who'd be happy to sell you one. The M166 is under $150.

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Just curious if you had to upgrade the alternator as well? I seemed to always be discharging slowly with all the accessories running on my dual-fan setup...
 

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Discussion Starter #4
Just curious if you had to upgrade the alternator as well? I seemed to always be discharging slowly with all the accessories running on my dual-fan setup...

Good point. Actually I upgraded to a 3G many many years ago. I think with just 12.5amp draw you'd be ok, but I agree that upgrading is a good idea.
 

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Looks like a great fan and I may be ordering one for my falcon. How do you find the noise of the fan? In the video it seems quite loud but it could just be the video. How does it compare, noise wise, to other electric fans that you've heard or have experience with?
 

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I just installed this fan in my Fairlane this past weekend. I thought it was pretty loud when compared to other fans, but not horrible. Installation was easy. I bought the fan, and thermostat/wiring harness from The StreetRod Catalog The Street Rod Catalog. Street Rod Parts Online.
price was $110 for fan and wiring harness/thermostat plus shipping.

Incidentally, my fan did not include the "nice rubber washers" that were included in Admin's writeup. Weren't anywhere to be found in the box.
 

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Nice article, I appreciate the information. I have been running an electric fan in my 73 Mustang for around 10 years myself and for many reasons it's one of my favorite upgrades. In my 73 space isn’t a real issue so I have always looked for the best CFM’s and biggest diameter I can get.
Here is some information I would add.
Since I built the motor that is in the car now I’ve only used an electric fan and at first had some overheating issues especially running the AC in the summer. I believe that was not the fault of the electric fan but due to the performance upgrades in the motor, thinner cylinder walls, and the headers adding heat to the engine compartment. At that time I was running a perma-cool rated at 2900 cfm with no built in shroud so I put my fan shroud back on and in my case it actually ran hotter I believe this was because the shroud restricted air flow more and didn't fit the fan the way the shroud was originally engineered to fit around the factory fan. The overheating was solved with a high flow water pump and high flow thermostat, smaller trans cooler to minimize restrictions, and adding an overflow tank. Also in the summer time running a mix of 20% antifreeze and 70% distilled water with a bottle of water wetter lower the temp a bit but a couple of summers after installing the HP water pump I found running a 50/50 mix in the summer worked fine.
I installed a Thermostatic fan control switch that turned the fan on when needed and off when not needed thus saving electricity and putting less strain on the charging system. Also if you think about it if you’re traveling at a speed that is moving air faster than the fan does the fan is just causing a restriction. Some may choose to hook the switch to a keyed power source but I opted to hook it to constant power straight off the battery that way it got plenty of juice and when I turned the car off it would continue to run until the radiator had cooled down. If I was overheating I would have a supply of cool water quickly. If you use this switch with a car that has AC it's mandatory to add a relay to make sure the fan runs constantly to keep air moving through the condenser when the ac is on otherwise you'll build too much pressure when you’re stopped and damage the AC system. I bought the whole setup at the local discount parts store chain and it was cheap and very easy to install. I think I’ve had to replace it due to failure once in the 10 years.
I did end up with a dead battery a couple of times so I replaced the stock 45 amp alternator with a 105amp and never had that problem again. I may have also bought a new battery then but I can’t remember for sure. But when you start adding modern electronics like a new stereo, electronic ignition and such that should be considered anyway.
The one drawback I have found is that after market fans doesn’t seem to last more than a couple of years. I don’t even know how many fans I’ve been through in the past 10 years. I’ve used supposedly top quality fans like perma-cool, flex-a-light, and derale and cheap $50 new fans bought at swap meets but can’t seem to get more than 2 or 3 years out of them. I will say I do drive my car a lot in the summer but I still expect more than I have gotten. I think my next fan will be a factory Mark VIII fan as discussed elsewhere on this site. Maybe the factory fan will do a little better.
 

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Try Perma Cool's electric fans. Lower amp draw and higher cfm. I have two 14" controlled by Dakota Digital's fan controller. These cool my 10.6:1 347ci stroker (450hp) with ease.

_______________
1968 Mustang coupe
 

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I have used Perma Cool fans on my Mustang (high performance fans #19114) for 5 years with no problems. Also used the same fans on my 1975 Dodge truck for almost 8 years with no problems. Yes if they run constantly any electric fan, even factory will burn out. Also I never use any mixture other than WaterWetter by Red Line and the rest distilled water. I live in southern California and do not have overheating issues in bumper to bumper traffic.
 

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The first fan I used was a Perma-cool Turbo Flex High Performance fan with the aluminum blades and I had a thermal switch. It did do better than some but it only lasted me 2 or 3 years. Back then I did drive it every day and all over the country. I put a lot of miles on it. I was also having some overheating problems so the extra heat it was exposed to may have shortened its life. I live in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com
<st1:State><st1:place>Kansas</st1:place></st1:State> and we get some very hot summers. We also get very cold winters so anti-freeze is a requirement. The rule of thumb around here is a 50/50 mix.
 

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I would like to know the thickness off the rubber spacer washers that came with your fan so that I can make a set for the electric fan that I have.

thanks
 
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