Jeep cj fan clutches

Awhile ago, I replaced my stock fan with a flexlight(?) set up for better cooling on my '78 cj7. While it did help my cooling, the added noise under acceleration and higher rpms is a bit louder than I would like. Saw a thread saying some thing about using a stock H/D clutch off a large block Chevy for improved air flow. Anyone used this setup? I am not ready to go to an electric fan set up now, as I have previously not had any "serious" cooling issues. Just trying to keep things cool with a v8 under the hood on 100 degree days.

I would recommend the CJ HD fan and clutch setup and make sure you have a good fan shroud.

Can you elaborate on the difference between a stock and a H/D set-up? How does the clutch work to better cool the radiator? Is there a new fan required or can I use my old stock one? Where can I purchase such a thing?

There was an article in one of the magazines a few years back where they compared stock and several aftermarket fans on a CJ. The best they found was a clutched fan with 7 blades from an A/C equipped Wagoneer. Been running that setup on my Jeep for years without complaints, however a 7 blade fixed (non-clutched) fan from an early 70's Jav/AMX does cool my jeep better at low speed, but it is noisier.

Bob
tufcj

Sounds like a 7 blade fan with a H/D clutch may just be the ticket. I found where the H/D clutches run at 80-90% of belt speed instead of a lower speed for a stock clutch. The 7 blade fixed I have is just a little too noisey.

I would just start searching the junkyards. your bound to find a wagoneer in there somewhere

Have two at home just not sure that tey are 7 blade, but I think a H/D clutch could make a big difference.

snip from here

"Now, here is where some folks join in the fray with Heavy Duty Fan Clutches and Flex Fans and such. Kind of makes you wonder if enough consideration was given to the other areas of the closed loop system.

That this solution has worked for so many is a testimony to the fact that the closed loop system probably worked when the vehicle was new, but being twenty to thirty years old and bored over as most of our rigs are, problems are bound to crop up. Also consider the fact that the radiators most of us are using are probably not nearly new with some blocked passages, and the ole water pumps have impeller blades eaten by cavitations. That thermostat we just put in last year was a bargain for $3.87 at the local auto parts store, and the coolant is probably more like 80% antifreeze to 20% tap water. All of which has resulted in coolant dissolved solids and minerals and calcium deposits throughout the system over the years; it is no wonder that we spout off so about any kind of improvement at all.

So, adding that heavy-duty fan clutch gets just enough oomph to get us over the hump and is universally agreed upon as the Holy Grail of Cooling.

Well, it is not a bad idea, my ONLY problem with this solution is that if we address the engineering behind the Heavy Duty Fan Clutch we find that it is designed to prevent the fan from turning at the same rate of the water pump shaft. Regular duty fan clutches operate at about 50-60% of shaft speed, and heavy-duty fan clutches are in the 60-70% range. A severe duty fan clutch will operate at 90% of its shaft speed. All will slip much more as the temperature of the silicon cools down a bit at high speeds.

This gives quieter operation (no howling) and perhaps better gas mileage. Also at higher speeds, the fan is spinning more freely and thus it frees up horsepower and allows more air to flow through the front of the radiator. Which brings up another issue, air dams can build up so as to prevent some air entering the engine compartment, due to the raised height and flow path of air underneath our rigs. On some lifted vehicles, an air dam can from underneath the front bumper to the front engine area, thus making it harder for heated air from the radiator to escape, and thus affecting the bi-metallic spring on the front of the fan clutch. Removing the hood and driving around a bit will reveal this odd occurrence.

Once we put this into perspective, we realize that the fan clutch is in reality a boon to those systems that have been designed and are in the middle of their operational parameters, so that the clutch can slip when additional airflow may not be needed, or additional air flow may be available when required, by having the clutch engage the fan and not allow it to slip as much.

Of note on fan themselves, is that AMC originally stipulated a 19.5 inch 7-blade fan, probably around a 2-inch pitch.

I just wanted to throw some things out there to consider, before everyone just starts to tear into their rigs and throw parts at potential problems, plus share some of the things that I have observed along the way."

In the middle of the last trail-ride, the fan clutch decided to spray silicone all over (again) #-o (Seems my pile of used junk has run out)

I plan on installing my new Hayden (P/N 2797) Severe Duty Fan Clutch tomorrow (runs 80-90% of water pump speed). Hopefully this is the last clutch I put in and the extra noise does not cause me to shoot it.

Hayden P/N 2747 is a 100% bolt-on Heavy Duty fan clutch for AMC V8's and a myriad of others... It runs 10-15% slower than the severe duty when engaged.

If this does not work, I'm going to follow the crowd and go Tarus fan....... Anyone got a 500A alt? Maybe I could pilfer the batteries from a Prius?


:razz:

Now that the motor is back in and I have been running the jeep hard both crawling and with the "hammer down" in 93-100* temps, I can say that the seven blade fan with the H/D clutch is keeping the engine cooled with no signs off over heating.

Now, I do also have an aftermarket radiator/flowkool pump and "wetter" in the fluid. But, it is nice to know that a seven blade fan will do the trick even in the heat of AZ.

Here is my post from the engine forum. the 2747 is fine but the 2797 is a done deal severe duty clutch that has not failed me yet. combined with a higher pitch fan and larger diameter fan. CJ's come with the stock 7 blade fan but there are better options with higher pitch. this combo worked in moab in 100+ weather 4x4ing in pritchet canyon, CA in the central valley with higher humidity and 100+ and in phoenix on the highway. though at highway speeds i think my flow cooler cavitates and heats up over 3000 rpm but then again 4.56 gears are my nemisis

"
People talk about it, people allude to it but no one ever seems to post the specifics. heres what has worked for me in pretty hot central valley CA temps 100+ in the summer.

For $269.76 this combo keeps a warmed 401 reasonably cool in the summer.


Engine fan:
For engine fans that fit the stock shroud and suck lots of air.

1. early 1970s - late 1970s Cadillac eldorado and others running 472s and 500's came with an 18" in diameter and 3-1/4" high pitch 7 blade fan
2. also there is the 1981-1986 Cadillac with the 4.1L v8 it is 7 blade an 18 inches in diameter also with similar pitch right at 3" -3-1/8" and moves a lot of air. It is unique in that it as a reverse bend on the top of the blades easy to spot.

I picked up one of each for $5 a piece from pick and pull so $10 total they both seem to pull the same amount of air. pretty incredible difference. I ended up running the old el dorado fan because it was the second one i installed. Its moving a TON of air at idle now. I was going to install an electric fan. now i am not going to bother

Fan Clutch:
For the fan clutch I used a Hayden Severe duty fan clutch #2797 (buick with the diesel in the early 80's on some models like napa i had to notch the holes just a smidge to clear the bolts into the water pump but on a summit model i didn't, it was slotted deeper with universal slots). $48.79 from my local napa

For Shroud:
Stock CJ7 V8 shroud (stock no cost)

For Radiator:
For an aluminium bolt in radiator i so far have only found 1 that is really a bolt in dont change anything else option. Everything else is cross flow and requires a different shroud and radiator hoses which is fine but i didnt want to spend booko bucks and change too much at once.
Go to ebay type in "3 row aluminium jeep radiator" up will pop 20 adds for a down flow design radiator made by champion radiators. it bolts in, it fits and it cools better than the extreme 4 core radiator i got from extreme radiators. I paid $139+ $30 shipping it has 3 rows of 5/8" cores. a little less than the 2 1" cores of many of the cross flow radiators but it seems to be doing the job so far. I would like to some day later find a radiator with a 1" taller core and dual 1" tubes but thats splitting hairs when you look at what this el cheapo aluminium radiator costs compared to other options.

For a thermostat:
Combined with a 180 mr gasket or robert shaw high flow thermostat $14.21

For coolant:
I run 30% dextron synthetic coolant and 70% Distilled water with 1 bottle of water wetter $32.87

Water pump:
Flow cooler water pump $89.95 (i already had one since my old water pump puked i did not include this in total price since most guys i know have em already on their jeeps)



Few details on the jeep. CJ 7 mildly warmed 401, t18 D300 4.5" spring lift, 35's, 8274 winch and winch plate in front, 1" body lift.

I have a 1" body lift which put the stock 7 blade 17" fan right close to the shroud. To clear a bigger fan and to help with geometry when lifting the tranny I moved the MORE motor mounts up and that created ample room clear the 18" fan in stock shroud. Since i was going for a flat belly pan with my clocked dana 300 things needed to be shifted little any ways i re=drilled the more mounts 7/8" up and 3/8" for ward sliding the motor slightly ahead helped with valve cover clearance at the fire wall, moving it up allows you to continue using the stock radiator shroud. I only re drilled one hole, lifted the motor up slid two bolts in (one from each side) and then proceeded to drill out the other 5 holes. you will only be able to use 5 bolts the 6th hole is too close and wont clear a nut. i reused the factory frame cross bar on the lower holes. also much over 7/8" will not give you enough material to bolt to on the bottom 2 or 3 holes. FYI My flat belly pan is actually 5/8" below my frame but that is fine for what i wanted. I would not move it any further forward you will have shroud fan contact issues.


Tests so far:
In my garage with no air flow at 94 outside degrees and inside 95+ degrees with the jeep running for 30+ minutes or longer heating up the garage, front of the jeep facing the rear wall and 2' away from the wall. the jeep at idle does not get past 195-200 degrees idling and being rev'd for an hour at a time dialing in the idling characteristics of the TBI it still did not climb over 200, sustained 2000-2500 rpm in the garage for 10+ minutes it saw 210 then crept back to 200. it used to clear 220-230 no problems idling and at highway speeds used to hoover at 215-220. driving around in 95 degree weather never saw over 205 even on the highway around on city street maintains 195-200




As a side note:
I also changed to a high zinc full synthetic motor oil 20/50 and found i did shed another 5+ degrees in engine temps at highway speeds and it looks like i may have dropped some temps in lower situations also not much but noticeable. I run a 20/50 around here even in my fresh motor summer time we regularly see 90-100+ days on the trail and around town. with 10/30 or 15/40 my idle oil pressure drops down to 12-15 psi at 200 + degrees.

I have nickle timing cover, mid plate, HRC gears valley oil bypass line and small cam bearing holes with 7.5 qt oil pan. engine at 200-220 degrees maintains 20-22 psi at 600 rpm with dino oil, with the synthetic 23-25 psi at 600 at 1200 rpm+ it jumps to 55-60 psi no matter what.

Update:
Air flow wise under the hood i decided to cut in and add a few louvers. temp wise it hasn't changed much but it cant be hurting you can really feel the air coming out now.

update 2:
I recently pulled a dead FJ40 with broken t-case adapter on 38;'s out of fordyce at night from winch hill 3 to the top at mid throttle and working the jeep 80+ degree weather and with all that pulling and the last hill at 3500+ and close to WOT never saw over 200-215 degrees with a full load behind me

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