What kind of fan are you running?

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The main thing to remember about that 1/2 hp of drag is that it's not there all the time. Takes that much to turn the weight of a clutch fan even with the clutch disengaged, I bet. 

I'm running adjustable temp probes, the kind with a ~3" probe on the end of a coiled solid wire. I have the probes pushed in the fins, not just strapped on the back of the radiator as the instruction say. Seems to work better in the radiator, but make sure you have them fixed in somehow! I have them close to the lower hose connection, near one of my fan attachments (I have the fan on the radiator using those through the radiator zip-tie like things). Didn't, and one slide out, keeping fan off until way past when it should have run, so temp started creeping up in slow traffic/at lights. If the probe goes all the way through a small zip tie around the end at the front of the radiator works well. Can't get to that end with my AC condensor, so I just hooked the probe wire on the radiator attachment, which is very close. Don't kink that probe wire though. I'm pretty sure it's solid, but it's not real strong and a kink could cause a break later. Have been running one of these controllers since 2003, no issues. I have it trip a relay to power the fan, not running full fan voltage through the switch, though some do. 

I have two of them now, and a pair of 12" fans instead of the single 16" Taurus fan. Taurus fan wouldn't clear water pump once I installed a three core radiator, was close with the two core (and shroud had to be trimmed down to fit with the I-6). One fan is connected to the controller I used for the Taurus fan and comes on when AC is turned on. Second is on it's own controller. That way both aren't running with AC unless engine temp comes up, and both don't turn on at the same time. I have the second set to come on just slightly after the first. Haven't checked temps, set it to come on a bit after first at idle on a hot day. 

https://www.summitracing.com/parts/hda-3653/overview/

Edited by farna - Jun/16/2017 at 6:11am

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farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19676	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: Jun/16/2017 at 5:46am
	The main thing to remember about that 1/2 hp of drag is that it's not there all the time. Takes that much to turn the weight of a clutch fan even with the clutch disengaged, I bet. I'm running adjustable temp probes, the kind with a ~3" probe on the end of a coiled solid wire. I have the probes pushed in the fins, not just strapped on the back of the radiator as the instruction say. Seems to work better in the radiator, but make sure you have them fixed in somehow! I have them close to the lower hose connection, near one of my fan attachments (I have the fan on the radiator using those through the radiator zip-tie like things). Didn't, and one slide out, keeping fan off until way past when it should have run, so temp started creeping up in slow traffic/at lights. If the probe goes all the way through a small zip tie around the end at the front of the radiator works well. Can't get to that end with my AC condensor, so I just hooked the probe wire on the radiator attachment, which is very close. Don't kink that probe wire though. I'm pretty sure it's solid, but it's not real strong and a kink could cause a break later. Have been running one of these controllers since 2003, no issues. I have it trip a relay to power the fan, not running full fan voltage through the switch, though some do. I have two of them now, and a pair of 12" fans instead of the single 16" Taurus fan. Taurus fan wouldn't clear water pump once I installed a three core radiator, was close with the two core (and shroud had to be trimmed down to fit with the I-6). One fan is connected to the controller I used for the Taurus fan and comes on when AC is turned on. Second is on it's own controller. That way both aren't running with AC unless engine temp comes up, and both don't turn on at the same time. I have the second set to come on just slightly after the first. Haven't checked temps, set it to come on a bit after first at idle on a hot day. https://www.summitracing.com/parts/hda-3653/overview/ Edited by farna - Jun/16/2017 at 6:11am
	Frank Swygert

one bad rambler Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2008 Location: On The Island Status: Offline Points: 2007	Post Options Post Reply Quote one bad rambler Report Post Thanks(0) Quote Reply Posted: Jun/16/2017 at 5:50pm
	The engine masters test was good but they never showed a true flex fan...Disappointing they should have known better... the plastic fan as well as the flex appearing fan are just pure crap..and the fixed fan is for low rpm use...Anything i use on the street i use the biggest flex fan that will fit..With a 2 row radiator..I`m a realist couple of hp loss so i can sit in traffic on a 90 to 95 deg hummed day and my temp never rises above 185..Watch the fan blades on this engine no way its using 20 to 30 hp it`s almost flat at 3,000rpm https://youtu.be/6PYwexfmqe8
	68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8

ARIZONAAMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Jun/15/2013 Location: Kingman, Az Status: Offline Points: 81	Post Options Post Reply Quote ARIZONAAMX Report Post Thanks(0) Quote Reply Posted: Jun/16/2017 at 9:32pm
	I tried several electric fans on my 68 AMX,although the coolant temp was okay,there wasn't enough airflow in the engine compartment at idle or low speed.The factory seven blade fan pulls alot more air to cool the engine,but I live in Arizona & it is going to be 110 degrees tomorrow.
	68 AMX 401,727.

ccowx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510	Post Options Post Reply Quote ccowx Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 1:03am
	I agree with you on the factory fans. I have a mild 390 with a two core rad and the metal shroud with the 7 blade fan and it cools awesomely. I have idled for an hour plus in border lineups and no issue at all. It moves a heck of a lot of air, even at idle! I suspect from watching those videos that I am losing probably around 20 horse though. Chris

FSJunkie Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742	Post Options Post Reply Quote FSJunkie Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 1:35am
	AMC designed their cooling systems well. The planet isn't much hotter now than it was then. They knew their cars would have to endure 110+ degree heat in many places in the United States. Most of this country sees 100 degree heat in the summer. They designed their cars, and their cooling fans, to be adequate for that. The belt-driven fans cool well. They may take a lot of power in some cases depending on their design, but they definitely seem to move quite a bit of air. It's been my experience that AMC engines (stock and with their stock cooling system anyway) run coolest at idle or low speed. Increasing load or RPM makes them run progressively hotter. That pretty much tells me that the belt-driven factory fans are doing their job, even if they take a lot of power sometimes. You should see the cooling system on my Buick 231 V6. It has a 3-row radiator taller and wider than anything AMC ever used and it has a 24", seven blade thermal clutch fan with full shroud. It's a little bitty engine with a gigantic fan and cooling system. It runs cooler than any engine I've ever seen.
	1955 Packard 1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited

tyrodtom Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6213	Post Options Post Reply Quote tyrodtom Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 9:17am
	My J-10 runs cooler at highway speeds ( 55-65 mph) now without the electric fan running, than it did before with the stock fan. But the fact that a J-10 front end is shaped sort of like one big scoop might have some influence on that. But I noticed the same on my 69 American, and 74 Hornet , your engine turned fan slows down the air flow through the radiator core at higher speeds. That fan is acting like a big solid disc right behind the radiator core. Years ago Car Craft, or Circle Track did the similiar test on fans, their results weren't quite as dramatic, like a maximum of 15-20 hp at 6000 rpm by the fans they test on a SBC. I've been running electric fans only on all my cars, trucks, and race car, since the middle 80's. I've noticed besides the usual benefits, better mileage, it is enough to notice, but also water pumps seem to last longer, ( if you keep a car long enough for this to matter) . You will never notice how much engine noise is due to that engine turned fan until you go electric.
	66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.

amcenthusiast Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778	Post Options Post Reply Quote amcenthusiast Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 10:43am
	OH they're full of hot air!... hee hee hee (just kiddn) Good topic for debate because rule of thumb thermal efficiency says 'only about 1/3 of engine heat is actually used to make power' = how to make the whole system more efficient. Missing information? Pulley diameters Water pump impeller design Noise factor Total operating cost Safety Durability any others? -------------------------------------------------------------------------------------------------------------------------- Trivia? -my former boss's '80? Ford van used a second barrel fan on it's HVAC blower fan motor with thermostatic switch to cool the engine (4.9 liter inline six, in small engine compartment) (the interior ventilation blower fan was made to serve double duty... dual purpose while A/C is turned on) -it would run on it's own after turning the engine off to cool the engine down to the preset temp... similar to a radiator mounted fan does on 'new cars' -the second side of the blower fan had it's own unique ducting Edited by amcenthusiast - Jun/17/2017 at 5:16pm
	443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc XRV8 Race Parts website: http://amcramblermarlin.1colony.com/

amcenthusiast Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/02/2012 Location: SW Atlanta GA Status: Offline Points: 1778	Post Options Post Reply Quote amcenthusiast Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 10:46am
	Wow thanks tyrodtom "That fan is acting like a big solid disc right behind the radiator core." (the flex fan flattens out) ...never thought of it that way Edited by amcenthusiast - Jun/17/2017 at 10:50am
	443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc XRV8 Race Parts website: http://amcramblermarlin.1colony.com/

Red Devil Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743	Post Options Post Reply Quote Red Devil Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 11:25am
	I pity the poor automotive "A"-section V-belt that tries to transmit 20-30 hp running a fan ... plus the water pump and alternator loads ... Main advantages of electric are independent control or fan speed vs engine speed so can be a more efficient overall design (even accounting for losses driving an alternator and electric motor vs direct drive), can shut off 100% when not needed and vary speed according to cooling requirements, keep on for cool down after engine shuts down (especially good for turbos), maintains consistent clearance to shroud for better efficiency (not affected by engine movement on it's isolation mounts), allows better packaging options for radiator and fan. I'm running a later thermostatic clutch fan - not as efficient as electric, but was simpler to fit and quieter than the direct drive fan. Noticed a very slight increase in mpg over the stock flex fan. If clutch fails again, may go electric.

Ken_Parkman Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814	Post Options Post Reply Quote Ken_Parkman Report Post Thanks(0) Quote Reply Posted: Jun/17/2017 at 1:02pm
	The thing is aerodynamically a fan cannot deal with the rpm range of an engine. It has to be designed to pull enough air at low engine speed to deal hot idling in a traffic jam; and to do that it is way way way wrong for higher rpm. That is why a mechanical fan is so spectacularly inefficient and really wrong for use on an engine. Flex and thermostatic fans are simple a band aid on a bad design, although a thermostatic is fair. But a basic mechanical fan is cheap. Iv'e put an electric on anything I consider a toy for the last 40 years. It is simply a win in every way, more power, better fuel efficiency, quieter, easier on the engine, and more correct for the cooling requirements of a car. Another huge advantage if you go to the track is the better ability to control the temperature. Although there are a couple of pitfalls to watch out for, You need to make sure the rad has enough airflow on the highway, and you need enough fan coverage to work at low speed.