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How do I determine electric fan CFM needs? #2942524
07/13/21 02:03 AM
07/13/21 02:03 AM
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jbeintherockies Offline OP
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Hello,

I'm trying to figure out how much CFM I need to pull through a big block Chrysler Summit 4-core radiator (radiator link) to keep a street/strip 440 cool. Is there a formula to use (ex: engine HP to BTUs)? I read a good rule of thumb is to have fan(s) that can pull 2500cfm for an 8-cylinder (how to choose an electric fan). I was looking at this shroud and fan combo from summit racing (kit link). However, it advertises only 1500cfm, which may not get the job done. I am trying to help my dad; it is his car.

The car is a 1967 Plymouth Satellite with a street/strip 440, Indy EZ440 heads, .530/.232@050, 10.8 comp, 22 degrees initial/37 total timing (we are in Colorado and he uses race gas), auto, 4.10s, flowkooler pump, 160 thermostat, factory fan shroud with a flex-a-lite fan (no viscous clutch installed; but he has one that could be used). It is an original big block car, so it has the larger radiator core support opening. The trans cooling lines are going into an external cooler and then into the radiator. I am not sure why the guy who built the car went that route; but I may try to bypass the trans oil lines going into the radiator. That might help. I also need to check that the radiator cap fits the radiator neck correctly and the pulley sizes. The car overheats (230+) in traffic, but runs around 190 or so cruising down the road. I believe the issue is airflow.

Questions/comments/concerns/thoughts?

Thank you in advance.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2942533
07/13/21 05:38 AM
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A few suggestions and questions:

Read the very long “Mercedes electric fan” thread in the questions and answers.

Search for and read the Stewart Components cooling tips.

I assume you are at an altitude of 5000 feet and air temperatures in the 95 to 105 degree F range?

Will the car reach 230 degrees coolant temperature idling in your driveway on the hot days?

Has the car actually boiled over and ejected coolant?

What antifreeze make and water mix percent is presently being used?

It there a modification that prevents you using a factory stock fan?

You might ask around among friends and family as to whether someone already owns a wind speed device like the Kestrel, and a good IR gun, preferably one that also has an external type K thermocouple probe too. If not consider purchasing these.

Re: How do I determine electric fan CFM needs? [Re: 360view] #2942541
07/13/21 07:25 AM
07/13/21 07:25 AM
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Just went through all the cooling problems with my Hemi Dart clone. Aluminum radiator, 165 thermostat, duel electric fans from the radiator builder claiming they would cool a 1000 HP engine. The car would climb to 230 degrees quickly. After going through everything to solve the cooling problems it turned out to be the fans were not pulling enough air. Put on a pair of 13 inch SPAL electric fans, mounted to a home made aluminum shroud. Now the car never goes over 190 degrees.Go on SPAL's website and pick the CFM rating you are looking for. The duel 13 inch low profile ones I bought pull 3560 total CFM and work great. I will not use any other brand after my experience. Search the internet for best pricing if your go with SPAL fans. Hope this information helps you.

Re: How do I determine electric fan CFM needs? [Re: maximus] #2942582
07/13/21 10:52 AM
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I've been down this road with my Cuda, so I'll make a few hopefully helpful comments: make sure your charging system and wiring is up to snuff. I highly doubt that the typical 79A Mopar alternator will cut it. The stock 12 ga charging wire will definitely not be sufficient, so start thinking about a higher output alternator and a much bigger charging wire. You also need to decide on your fan control system. Are you going to simply use a switch to turn the fan(s) on/off? Probably not the best idea for any sort of city driving, so think about what fan controller you want. There are many different options available.
Just wanted to mention these things, because they are often overlooked, but they are equally as important as choosing the fan(s) themselves. I can go into more detail about what I have done if you want.
Hope this helps.

Re: How do I determine electric fan CFM needs? [Re: 360view] #2942712
07/13/21 05:58 PM
07/13/21 05:58 PM
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jbeintherockies Offline OP
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Quote
Read the very long “Mercedes electric fan” thread in the questions and answers.

Search for and read the Stewart Components cooling tips.


Will do!


Quote
I assume you are at an altitude of 5000 feet and air temperatures in the 95 to 105 degree F range?


Around 5280, yes. Air temps are in the mid-to-high eighties F; not quite 95-105.


Quote
Will the car reach 230 degrees coolant temperature idling in your driveway on the hot days?


I don't know, never tested that


Quote
Has the car actually boiled over and ejected coolant?


Yes


Quote
What antifreeze make and water mix percent is presently being used?


I think it is Oreilley 50-50 mix. I know he has added "Water Wetter" and the VP Racing "Madditive" (Madditive link) additive.


Quote
It there a modification that prevents you using a factory stock fan?


None. But it the current factory stock fan shroud and flex fan aren't getting the job done, why do you think a switch to the factory fan would? I am not a fan (no pun intended) of flex fans. I run a factory setup on my small block barracuda and it works great. But I have a two-core radiator, not a four core. I can try the factory fan and clutch and see how it goes.


Quote
You might ask around among friends and family as to whether someone already owns a wind speed device like the Kestrel, and a good IR gun, preferably one that also has an external type K thermocouple probe too. If not consider purchasing these.


I have a Craftsman IR gun, but it doesn't have the external thermocouple probe. I think my voltmeter has a thermocouple probe; I'll have to check that.

Re: How do I determine electric fan CFM needs? [Re: maximus] #2942713
07/13/21 05:59 PM
07/13/21 05:59 PM
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jbeintherockies Offline OP
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Originally Posted by maximus
Just went through all the cooling problems with my Hemi Dart clone. Aluminum radiator, 165 thermostat, duel electric fans from the radiator builder claiming they would cool a 1000 HP engine. The car would climb to 230 degrees quickly. After going through everything to solve the cooling problems it turned out to be the fans were not pulling enough air. Put on a pair of 13 inch SPAL electric fans, mounted to a home made aluminum shroud. Now the car never goes over 190 degrees.Go on SPAL's website and pick the CFM rating you are looking for. The duel 13 inch low profile ones I bought pull 3560 total CFM and work great. I will not use any other brand after my experience. Search the internet for best pricing if your go with SPAL fans. Hope this information helps you.


Thanks, I will definitely keep your advice in mind if we go the route of electric fans.

Re: How do I determine electric fan CFM needs? [Re: mrob] #2942716
07/13/21 06:13 PM
07/13/21 06:13 PM
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Originally Posted by mrob
I've been down this road with my Cuda, so I'll make a few hopefully helpful comments: make sure your charging system and wiring is up to snuff. I highly doubt that the typical 79A Mopar alternator will cut it. The stock 12 ga charging wire will definitely not be sufficient, so start thinking about a higher output alternator and a much bigger charging wire. You also need to decide on your fan control system. Are you going to simply use a switch to turn the fan(s) on/off? Probably not the best idea for any sort of city driving, so think about what fan controller you want. There are many different options available.
Just wanted to mention these things, because they are often overlooked, but they are equally as important as choosing the fan(s) themselves. I can go into more detail about what I have done if you want.
Hope this helps.


All good advice. We are both well aware that the current factory square-back is not going to get the job done if my dad decides to go with twin electric fans. The charge wire has been upgraded already to either 10 or 8; I forget now. I was planning on using two relays to control the fans. The fan closest to the radiator inlet would turn on when the ignition key was set to the 'run' position. So it would always be running when the engine is running. I was going to use this relay setup (Hayden Auto Relay) to control the other fan and have it come on at around 185 or 190 degrees. I am aware of electronic fan controllers (ex: Dakota Digital electronic fan controller); but was trying to stay away from something like that.

I am curious, what shrouding and fan setup did you go with? Did you try hard to get a factory setup (factory shroud, factory fan, factory viscous clutch) to work before going electric? I am very much in favor of staying with the mechanical if possible; but I have my doubts that is going to work in this scenario.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2942749
07/13/21 07:46 PM
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jbe, in response to your questions:

Depending on the amp draw, 8GA or 10GA may not be enough. To give you an example: a popular Spal dual fan combo is P/N 30102052 and consists of dual 11 inch, 5 bladed paddle fans. At 0.6 inch pressure drop (basically the resistance through a thin radiator), they draw around 33A. Thicker radiator cores will draw more amps, so keep that in mind. On top of that the 33A draw is especially bad at idle when the alternator isn't spinning that fast. I don't know what all of your electrical loads are, but I ran 6GA cable from the alternator through a 150A fuse to the positive lug on the starter relay (which is connected to the battery).

Your idea about having one fan running all the time isn't bad, and only controlling the second fan with a temperature driven relay will definitely help lessen the "shock" of 2 fans kicking on simultaneously. I use the Dakota Digital controller that you mentioned to perform in a similar way. I set the one fan to come on at a low temperature and keep it running basically all of the time. The second fan just kicks in when the first fan doesn't cool enough (usually when idling).

I ended up with the Derale 16833 shrouded fan kit because it fits a 26 inch wide core pretty well. Beware, the fan cfm specs that Derale give are overblown! They claim 3750 cfm, but there's no way that's possible. I contacted the fan manufacturer about the fan specs and each fan is only capable of 1346 MAX cfm. So according to my math, that's around 2700 cfm total. Gee, that seems a bit less than 3750 cfm ...

I tried various mechanical fans. Different diameters, number of blades and blade pitches and none of them cooled my engine well at idle. The best combo was the 18 inch, 7 bladed Mopar fan with the thermal fan clutch. Even that fan wasn't enough to keep the temperature from creeping up at idle. There's nothing worse than watching the temperature gauge slowly creep up while you're sitting in at a stop light.

Hope this helps

Re: How do I determine electric fan CFM needs? [Re: mrob] #2942754
07/13/21 08:07 PM
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Flex fans do a real good job of not moving air. If you do have a stock fan to swap in, try that.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2942762
07/13/21 08:17 PM
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That is not a fan shroud, it is a air blocker.

Re: How do I determine electric fan CFM needs? [Re: 71birdJ68] #2942802
07/13/21 09:19 PM
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I have the Cold Case radiator and fan on my 528 Hemi with air conditioning. Stays nice and cool about 190 all the time.

Re: How do I determine electric fan CFM needs? [Re: mrob] #2942828
07/13/21 10:48 PM
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Originally Posted by mrob
jbe, in response to your questions:

Thicker radiator cores will draw more amps, so keep that in mind. On top of that the 33A draw is especially bad at idle when the alternator isn't spinning that fast.


That information is not quite correct. A thicker radiator with reduce air flow in most cases. Affinity laws state that for centrifugal loads like a fan, theoretical hp is the square of the flow and the cube of the rpm. That means that the power requirement (including amps) goes down quite a bit when the flow is reduced.

In addition, when you are idling, the voltage drops. Again the power is a cube of the voltage, so when the voltage drops the current drops quite a bit. Flow also suffers quite a bit.

In my race car, I went from a 55 amp alt to 120 amp. Gong down the track I went from 11.8 volts to over 13. Clearly the alternator was too small. The higher voltage increased fan and water pump speed to the point that on a hot day back at the pits car was 20 to 30 degrees cooler than before - usually around 20 degrees.


67 Coronet 500 9.610 @ 139.20 mph
67 Coronet 500 (street car) 14.82 @ 94 mph
69 GTX (clone) - build in progress......
Re: How do I determine electric fan CFM needs? [Re: 360view] #2942912
07/14/21 07:05 AM
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If you are going to get serious about fan work, in addition to IR-gun, accurate thermometers, and electrical multimeter,
you are going to need to measure tiny pressure differences with a mini digital manometer.
After reading Amazon reviews I took a chance on a $36 HT-1890 “no name” Chinese unit and it has worked pretty well. These also can be valuable evaluating the low pressures of exhaust systems.

Years ago we had to use inclined tube mechanical manometers, some of which were 6 foot long and had to be perfectly level to read accurately.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2943026
07/14/21 11:58 AM
07/14/21 11:58 AM
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Originally Posted by jbeintherockies
Hello,

I'm trying to figure out how much CFM I need to pull through a big block Chrysler Summit 4-core radiator (radiator link) to keep a street/strip 440 cool. Is there a formula to use (ex: engine HP to BTUs)? I read a good rule of thumb is to have fan(s) that can pull 2500cfm for an 8-cylinder (how to choose an electric fan). I was looking at this shroud and fan combo from summit racing (kit link). However, it advertises only 1500cfm, which may not get the job done. I am trying to help my dad; it is his car.

The car is a 1967 Plymouth Satellite with a street/strip 440, Indy EZ440 heads, .530/.232@050, 10.8 comp, 22 degrees initial/37 total timing (we are in Colorado and he uses race gas), auto, 4.10s, flowkooler pump, 160 thermostat, factory fan shroud with a flex-a-lite fan (no viscous clutch installed; but he has one that could be used). It is an original big block car, so it has the larger radiator core support opening. The trans cooling lines are going into an external cooler and then into the radiator. I am not sure why the guy who built the car went that route; but I may try to bypass the trans oil lines going into the radiator. That might help. I also need to check that the radiator cap fits the radiator neck correctly and the pulley sizes. The car overheats (230+) in traffic, but runs around 190 or so cruising down the road. I believe the issue is airflow.

Questions/comments/concerns/thoughts?

Thank you in advance.


Another data point: 1972 Dart, low-deck 451, .652/272@.050, 10.3 comp, 27 initial/36 total, 4-speed, 3.91, Flowkooler pump, 180 Milodon hi-flow thermostat, Champion 3-row 26" aluminum radiator, Ford Contour electric fans with Autocoolguy PWM controller.

Idles at 182 all day in 90+ degree weather. It does heat a bit on the highway (65 mph is 3300 rpm) and after 15 minutes it levels out at 198. Slowly comes back down once off the highway. This is probably due to the Contour fan shroud blocking airflow when the fans should not be needed at highway speed, but I can certainly live with temps at or below 200. Especially since it stays cool in stop & go (or just stopped) wink

Something to watch out for, besides the electrical upgrades which have already been mentioned: more small cores (4) is not better. All that metal interferes with the airflow and the multiple small tubes don't have as much heat transfer capability as fewer large tubes... IMHO the best radiator to use is a two-row with 1.25" or even 1.5" tubes if there is room between the core and the engine.

Chevy HHR fan is supposed to work well but I'm not sure it'd be big enough either. Also a Lincoln (Mark VII?) fan is a good one. But the Contour dual fan is cheap and readily available.

The additional trans cooler probably helps a bit, but I would not use it instead of the radiator cooler. It'd have to be pretty big depending on the converter... work

Last edited by DrCharles; 07/14/21 11:59 AM.
Re: How do I determine electric fan CFM needs? [Re: DrCharles] #2943093
07/14/21 02:12 PM
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Something to watch out for, besides the electrical upgrades which have already been mentioned: more small cores (4) is not better. All that metal interferes with the airflow and the multiple small tubes don't have as much heat transfer capability as fewer large tubes... IMHO the best radiator to use is a two-row with 1.25" or even 1.5" tubes if there is room between the core and the engine.


I like the two core radiators, too. But, my dad bought a four core and that is what I have to work with.


Quote
The additional trans cooler probably helps a bit, but I would not use it instead of the radiator cooler. It'd have to be pretty big depending on the converter...


It has a 10" converter. I will leave it as-is for now.

Re: How do I determine electric fan CFM needs? [Re: NITROUSN] #2943094
07/14/21 02:15 PM
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I have the Cold Case radiator and fan on my 528 Hemi with air conditioning. Stays nice and cool about 190 all the time.


What shroud? Electric fans I assume?

Re: How do I determine electric fan CFM needs? [Re: 360view] #2943096
07/14/21 02:20 PM
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a good IR gun, preferably one that also has an external type K thermocouple probe too. If not consider purchasing these.


What areas am I probing with the thermocouple probe, around the radiator core itself?


Quote
you are going to need to measure tiny pressure differences with a mini digital manometer.


How do I use a manometer? Where on the car would I be using it and when?

Re: How do I determine electric fan CFM needs? [Re: Sniper] #2943098
07/14/21 02:22 PM
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Originally Posted by Sniper
Flex fans do a real good job of not moving air. If you do have a stock fan to swap in, try that.


My brother has a factory fan not currently being used; not sure what diameter or blade count. I can try it with the clutch and see how it goes.

Re: How do I determine electric fan CFM needs? [Re: 71birdJ68] #2943099
07/14/21 02:24 PM
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Originally Posted by 71birdJ68
That is not a fan shroud, it is a air blocker.


Yea, cruising down the highway would probably result in HIGHER temps using Summit's "shroud". I'll keep looking.

EDITED: Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2943735
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All of my temperature evaluations start with a 1/8 " tubular thermocouple probe adapted into the intake manifold as close as possible to the thermostat. Do be careful not to BURY the probe against the bottom of the opening/port as it will impact the readings and sensitivity. This will put the probe in direct contact with the coolant as it is leaving the motor. The main reason for using Thermocouples is they are extremely accurate, sensitive, don't lie, nor do they need calibration. The meters may but rarely do unless abused.

You can buy extension leads to run inside the car and watch the actual temperature changes. most Digital multi meters today have a plug in for the T/C's. Make sure you get the correct type of probe and extensions for your particular meter. Type J and K TC's & extensions appear to be, BUT are not interchangeable and will skew the readings. Both types are available inexpensively on eBay or Amazon as well as various meters / DVM's etc. An example is of the probe is in the link just below this paragraph. I'm sure there are others and possibly less expensive. I use an 1/8" oil pressure line compression fitting and adapt it up to what ever size is needed. The metal portion is also bendable to a point but not on a repetitive basis. If you are careful and do not overtighten the fitting you can move the ferrule or carefully remove it to allow repositioning for the next use.
THERMOCOUPLE EXAMPLE LINKY

You may be surprised at things that affect the temperature, like a semi changing lanes in front of you and the temp starts ticking upward until you fall a good distance behind him. Going north on I-29 can make the temp climb a bit, while turning around and going south makes it drop. This is on what appears to be level ground.
These scenarios have repeated many times with different vehicle's over the years.
As we all know, gauges can be wrong for many reasons, IR guns are good for a general indication but they need to be calibrated for the surfaces / coatings they are reading as well as the distance from those surfaces there are many variables that can affect their accuracy.
keep us posted beer

Last edited by TJP; 07/16/21 11:56 AM.
Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2943815
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Originally Posted by jbeintherockies
Originally Posted by Sniper
Flex fans do a real good job of not moving air. If you do have a stock fan to swap in, try that.


My brother has a factory fan not currently being used; not sure what diameter or blade count. I can try it with the clutch and see how it goes.


Putting a stock fan in place without the viscous clutch would be a worthy experiment, especially if it is the 18 inch diameter/ 7 blade unit.

How would rate your own or nearby available metal working skills?

Could you cut down the outer edges of the blades of a 9 blade Ram/Dakota fan and find the equipment or shop to re-balance it?
Or re-drill the bolt holes of a Ford/GM/Toyota fan?

The purpose of the K thermocouple probe on an IR-unit is to be able to IR read the temperature of a spot,
then switch to a probe to touch that same spot and find out how off the IR reading was.
IR units with “emissivity” adjustment are also preferred for this reason.
Low end IR units have the emissivity set at 0.95 without adjustment.
Use your present Craftsman IR unit to scan your warmed up radiator and look for “cooler regions“ that might indicate internal coolant flow blockages.

Re: How do I determine electric fan CFM needs? [Re: 360view] #2944878
07/19/21 03:44 PM
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I was at a drag and drive event in June (Rocky Mountain Race Week) where a lot of guys were running the electric fan setups from an '06 Charger with Hemi engine. They said they were getting them from bone yards. They were putting them in twin turbo LS powered cars. I think if you can find something from an OEM vehicle, they are proven to work fairly well.


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Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2944984
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You haven't said what water pump drive you are running. Make sure you are spinning the water pump fast enough at least 1 to 1 with the crank. I have a little more engine in my Savoy and I'm running a 26" 3 row rad with an 18" thermo clutch fan. My pulleys are 440 source repo units with a Flow-Kooler high volume pump and my car stays around 180 on a 90 degree day on the highway at 3600 RPM. It does creep up around 190 when sitting at a light but that is not really hot. I haven't put a shroud on it yet but that would probably cure the low speed cooling around town. On the alternator you don't need a 100 amp unit but you could use a basic Toyota internal regulator alternator unit. The bracket kit and plug you can get from AR Engineering and I suggest a Factory Denso unit over a discount rebuilt unit from the zone or one of the other stores. They charge 14.5 volts at 900 RPM and do away with the failure prone firewall mounted regulator. twocents

Gus beer

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Re: How do I determine electric fan CFM needs? [Re: fourgearsavoy] #2947284
07/26/21 11:46 AM
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Originally Posted by fourgearsavoy
You haven't said what water pump drive you are running. Make sure you are spinning the water pump fast enough at least 1 to 1 with the crank. I have a little more engine in my Savoy and I'm running a 26" 3 row rad with an 18" thermo clutch fan. My pulleys are 440 source repo units with a Flow-Kooler high volume pump and my car stays around 180 on a 90 degree day on the highway at 3600 RPM. It does creep up around 190 when sitting at a light but that is not really hot. I haven't put a shroud on it yet but that would probably cure the low speed cooling around town. On the alternator you don't need a 100 amp unit but you could use a basic Toyota internal regulator alternator unit. The bracket kit and plug you can get from AR Engineering and I suggest a Factory Denso unit over a discount rebuilt unit from the zone or one of the other stores. They charge 14.5 volts at 900 RPM and do away with the failure prone firewall mounted regulator. twocents

Gus beer


Interesting you should ask : )

I worked on the car over the weekend. Once I had the radiator and fan out, I noticed the crank pulley was very small. I then measured its diameter and compared it to the crank pulley on my brother's 67 GTX. Sure enough, my dad's crank pulley is a 5" underdrive unit. The crank pulley on the GTX is about 6-1/2" in diameter. I read that the 5" crank pulley underdrives the accessories (only WP/fan and alternator on this car) by 30%! That explains why the volts drop when he comes to a light and most likely why he is having so many serious cooling issues.

So, I will be buying a repo crank pulley from 440 source. I am also going to buy an overflow/recovery tank and a fan.

Speaking of fans, my brother doesn't have a fan to use. So, I was considering either of these:
Derale 19" 6 blade clutch fan
Mancini Resto 18-1/2" 7 blade clutch fan

The price of the resto 7 blade is insane. But it might be worth it if it cools (and is balanced) better than the cheap Derale. I will be using a new viscous fan clutch because that is what my dad has available to use.

Thoughts?

I took the radiator to A1 Radiator in the Denver area to have him pressure test it along with two different caps; it was steaming the last time the car overheated. I think the steam was coming from the top of the core; but I couldn't get a good look of where it may have been coming from because of the shroud. I also was in a hurry when I took the radiator out to get to the shop before he closed on Saturday. So, I didn't have a chance to remove the shroud and do a thorough investigation.

I have a good voltage tester with a thermocouple and a laser temp gun. I haven't bought the anemometer yet; they are expensive. Yes the manometer that was suggested ($36 HT-1890 “no name” Chinese unit and it has worked pretty well) is cheap; but I'm not sure I really need it.

I've been looking into upgrading the alternator. I am waiting to see if I can get this car cooled with the factory setup before I choose an alternator. The Denso's are cool, but are more money and require a different bracket setup (AR Engineering) and a plug/pigtail (i.e., even more money). The Powermasters (which I have on my car), bolt right in. My Powermaster alternator has been great! I would only buy a new alternator; I wouldn't buy a rebuild from any of the parts stores.

Last edited by jbeintherockies; 09/11/21 06:55 PM.
Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2947686
07/27/21 09:09 AM
07/27/21 09:09 AM
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Rittman Ohio
fourgearsavoy Offline
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I would find a used fan local or on the web and use it with a new thermal viscous drive. I was just at the Monster Mopar swap meet over the weekend and there must have been a dozen fans at the small swap meet they have so they are out there used.

Gus beer


64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60
Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2947697
07/27/21 09:38 AM
07/27/21 09:38 AM
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360view Offline
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What is the size of the opening in the shroud?
Probably also ought to carefully measure if the center of the present fan is in the exact center of the shroud opening.

A ten percent larger diameter fan does not move 10% more CFM.
It typically moves
1.1 x 1.1 x 1.1 = 1.33
at least.

The power taken from the engine typically increases even more
1.1 x 1.1 x 1.1 x 1.1 = 1.46
or 46% more

Above assumes fan design and number of blades at pitch angle
stays roughly constant

Power laws of fans routinely surprises

The bending of blades in a flex fan make them unpredictable especially as age makes the material either stiffer or looser.

In past posts here on Moparts is a graph of rpm versus kilowatts comparing the solid fan versus viscous clutch fan of the original 340 V8

The plastic multibladed radiator fan of later model year Cummins Diesel Ram trucks looks like a computer aided design that might be significantly better than older designs.

Re: How do I determine electric fan CFM needs? [Re: 360view] #2947706
07/27/21 09:49 AM
07/27/21 09:49 AM
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360view Offline
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not sure of diameter

07C8219A-BF43-417E-9E34-1926BA22C319.jpeg
Re: How do I determine electric fan CFM needs? [Re: 360view] #2947710
07/27/21 09:53 AM
07/27/21 09:53 AM
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360view Offline
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another non oem

70541814-8471-4C58-B815-8B9E680379C4.jpeg
Re: How do I determine electric fan CFM needs? [Re: fourgearsavoy] #2947851
07/27/21 04:48 PM
07/27/21 04:48 PM
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Originally Posted by fourgearsavoy
I would find a used fan local or on the web and use it with a new thermal viscous drive. I was just at the Monster Mopar swap meet over the weekend and there must have been a dozen fans at the small swap meet they have so they are out there used.

Gus beer


iagree with Gus. When I had the aluminum headed 340 in my Dart it had overheating issues. Brand new 22" copper radiator, 160° high flow thermostat, new WP and a Flex-A-Lite Black magic electric fan. Thought the radiator was the issue so I installed a generic 22" aluminum radiator, Flow Kooler WP, my electric fan was too deep so I bought another, still ran hot. I thought there was a issue with the engine and was going to take it apart to inspect it, someone here recommended that I try a belt driven fan with a shroud. Luckily a buddy of mine had a like new MP viscous fan kit that he sold me cheap. I cut down a shroud off a 26" radiator to work on the aluminum radiator, used the high flow thermostat and Flow Kooler WP. My overheating issues went away. It's never been anywhere near hot since then. The car currently has a pump gas 434" small block in it that has gone 6.25 in the 1/8 and never gets hot on the street or at the strip.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2962211
09/08/21 03:51 PM
09/08/21 03:51 PM
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Aurora, CO
jbeintherockies Offline OP
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Update: So I bought a 5-blade, Mopar performance fan from my friend Jim. I also bought new crank and water pump pulleys from 440Source and Hayden's low profile heavy duty thermal fan clutch (I regret buying the clutch; I should have simply tested this using no clutch like what was suggested). The reason I bought a new water pump pulley is because the aluminum one that was on the car was so thick there was barely any space to mount the fan clutch and fan. I first tried used pulleys that I got from my friend. But the water pump pulleys that I got in the deal didn't fit (either hit the water pump or did not align properly). Also, the crank pulley that I got in the deal didn't fit because the balancer on the engine is modern, requiring the pulley with the offset. So, out of frustration, I simply bought new pulleys. Prior to installing everything, I spent a lot of time sealing the factory fan shroud to the radiator, using strips of neoprene that I attached using rivets and silicone to seal the bottom of the shroud, where a large gap (1.5") existed. The car was out last weekend at the Golden Super Cruise and it still ran hot; got to 230 while sitting in traffic. So, after all of this, I fixed nothing.

At this point I guess I can try the 7 blade factory fan. The Cummins diesel fans are huge and would require modification to fit into the shroud opening. My friend did have a large fan from a 70's Ramcharger; but way too big for this application. Regarding the suggestions of trimming down these large fans, I think the ends of the fan blades are shaped in a specific way (looks like it to me). If I start trimming them down, I will most likely disrupt the flow of air off of the fan blade tips.

Finally, I am not convinced that dual electric fans are going to fix the issue. My friend Jim runs a 500 on the street with 13.5 compression and a .700+ mechanical roller and the Mopar performance fan with viscous clutch keeps that "cool" (around 200). This engine is making a lot less power than that one makes. The specs of the car and engine applicable to this thread can be found in the first post of this thread.

Last edited by jbeintherockies; 09/08/21 04:38 PM.
Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2962453
09/09/21 12:02 PM
09/09/21 12:02 PM
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north of coder
moparx Offline
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what radiator does your buddy with the 500 use ?
beer

Re: How do I determine electric fan CFM needs? [Re: moparx] #2965263
09/18/21 03:22 PM
09/18/21 03:22 PM
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Aurora, CO
jbeintherockies Offline OP
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Factory 3-core. The engine now runs on E85, which makes it run cooler. he said it ran hotter on race gas.

Re: How do I determine electric fan CFM needs? [Re: jbeintherockies] #2965268
09/18/21 03:37 PM
09/18/21 03:37 PM
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nowhere
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Originally Posted by jbeintherockies
Factory 3-core.


And you are running an aftermarket aluminum 4 core.

Seems we found the issue there. Maybe your buddy can help you play swap with his stuff to see what's the issue.

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