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.
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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.
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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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<embed src="http://www.youtube.com/v/G9qZnq_Cj3U&hl=en" type="application/x-shockwave-flash" wmode="transparent" height="355" width="425"></object>
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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lace>Kansas</st1
