Has anyone changed out the old clutch for a light weight fan? What are the benifits of a clutch fan over a light weight aluminium fan??

 

What's a clutch fan?

 

A clutch fan is the one you can spin with the motor turned off. It freewheels when the engine reaches a certain temp and RPM.
So it's not drawing power off the engine at high speed because the engine gets cooled by air at speed. Only benefit of a flex/fiberglass fan is less weight. The offset is it's noisier.

Dep

 

Well technically it's a fan clutch. That's the piece between the waterpump and the fan that allows the fan to freewheel at higher engine speeds reducing the load on the engine.

Here's a pic of one I found on the net.

 

Well if you REALLY want to get technical, it's a declutching fan assembly when you add the fan blades.

Dep

 

I have a belt driven clutch fan and an electric fan on my '82. I removed the belt driven fan and connected the 2 wires from the temp sending unit so my electric fan stays on at all times. I'm sure I freed up a few ponies and my Vette still runs cool.

 

I put an aux fan from an '81 'Vette and tried to run with just that--forget it, temp shot up fast. Everything in the cooling system was new including the engine. I wonder what the difference is?

 

OK you guys convinced me. I'm ordering a new fan clutch from NAPA for $51.00 + tax and forgetting about the light weight Aluminim fan.
Even my 75 year old uncle who a car guy told me "you know GM didn't hire a bunch of monkeys for engineers" "those guys know what they're doing son"

I was just looking for more HP's and less weight. Hey I'm a guy that's what guy's do?

Oh and the person running hot I added sub-zero from ecklers and I never run above 200*

 

The performance books actually endorse the "declutching fan" option.
Note that my 2004 Silverado has a pastic fan AND the fan clutch on it. So it saves weight AND HP.
Pretty cool

Dep

 

I tried to put one of those nice plastic fans on my '77--too bad the fan turns the wrong way...

 

Bummer

Dep

 

No, all you did was turn a minor intermittant load from the fan clutch into a constant load on your alternator that now has to supply power to run the fan all the time. You actually took a step backwards in power.

Fan clutches absorb nearly zero power when not required to turn the fan. It is NOT a performance upgrade to ditch them for electric fans.

 

That is partially, at least.

Fan clutches OR clutchless flex fans at higher rpm pull little power. On the other hand, electric fans don't pull anything off of the flywheel. Energywise, anything that is pulling power only when needed is a boost to the system's efficiency. However, all the wasted power from an always-on electric fan is only from the battery, mandating the alternator be under a load more often.

I do not know how much different breaking resistance drag the alternator produces when it is actually supplying current, but I believe it is different from when it doesn't detect the need for current (i.e. I *think* it's harder to turn when the circuit is on and deriving current from it than when it does not, although I s'pose it's possible it has the same pull all the time and the generated current is just switched to not go to the system when it's not needed.)

In any event, the drag from the alternator hits the flywheel less than the drag from the fan moment to moment, but the same overall from the perspective of system energy perspective. Any difference in mechanical connections not losing some efficiency compared to electrical power generation also factors in there (either way you need the belt with a mechanical water pump.)

One serious concern I have always had on electric accessories such as fan, fuel pump and water pump is switching reliability and functionality when battery or alternator are malfunctioning. Long ago I switched to HEI ignition though, so I guess I ultimately decided screw the "works better under more broken down condition option" and risk being sidelined for a bad alternator. One day I will switch to one of the higher powered electric water pumps too.

Those auxilliary fans are excellent for fixing low air flow at idle and minimize the 20-25 degree climb after engine shutdown. I bought an aftermarket 12-14" one that flows about 1400 cfm or so (if I recall), but I later decided to go all out and do another new radiator (DeWitts) and all e-fans (a 16" premium, 9" and 8" - totalling 6500 cfm.) The radiator got here today!!!

The SPAL (and now Zirgo) fans pull 2500-4,000 cfm on their 16" premium models.

------

BTW, from the perspective of someone who only ever bought ancient junkers and lived in a hot climate, I always ditched the factory clutched fan, which fail when old, in favor of the best flex fan I could find and went with the lowest temp thermostat or without on engine designs that can take it (neither SBC nor BBC can run without a thermostat.) Yet with all parts new, a higher running temp and a fan clutch are good things.

 

No flex-fan for me!

I had a Haydon for three months when it exploded! I has steady cruising on the Interstate at 70mph when 3 of the blades let loose. They went right through the fan shroud like hot razors through butter-the holes they made had perfect airfoil shapes! I was lucky none flew off in the direction of the hood! Hoses and belts all sliced up. It was a mess.

Haydon examined the fan and determined it was a factory defect and treated me very very well.

But now I'm scared of them.
-----------

I have my aux fan wired up so it comes on when the a/c is on AND the break pedal is pressed (with a 20 second on-break delay). This is the surest way I thought of to allow the aux fan to run while the 'vette is either stopped or in slow speed traffic only. I didn't want it to run while cruising at speed.

It also comes on at 210F coolant temp and is manually switched as well.

 

If this is the case, then why do the LT1s (Designed at least 10 years after my '82) and most subsequent engines, have electric fans and water pumps?

The electric fan may pull a constant load but at least it does not pull a higher load at high RPMs as belt driven fan does. This is actually reverse of what the engine needs, i.e. more cooling at higher speeds. Most cooling is needed sitting at an idle with no air ram air effect.

I did see a .3 sec improvement in the 1/8 mi after removing the belt driven fan, but I also had just installed my dual air cleaners.

Based on the gauge of the wires, it doesn’t look like the fan could draw many more amps than the lights. Do you run a better time with your lights off?

Just some food for thought....

 

I ran electric fans for a year. Here is my experience:

Good Points:

1. Frees up a lot of room in the engine bay.

2. They do improve fuel economy on the highyway by at least 2 mpg--my 'Vette pulls 3000rpm at 70mph--so that's a reason for the improvement.

3. Makes the car rev and drive a whole bunch smoother.

4. Quiets the mechanical underhood noise.

5. Does free up power on WOT--less spun mass.

Drawback:

1. Very high underhood temperatures--the electric fans don't blow enough air to cool anything but the radiator--everything becomes RED hot. Not good for a/c and the extended life of underhood components.

That one drawback was enough for me to go back to the fan/clutch.

 

Not true Clint. The belt-driven declutching fan freewheels at highway speeds. So there is very little drain on the engine.

Dep

 

That may be true on other cars--cars with upright radiators. There just isn't enough air going through our radiators, even on the highway, to cool C3's. Those of you with electric fans, head out on the highway and turn off the electric fans. And, see what happens--temperature will rise fast!

I have heard people say this before, but my 'Vette can't run on the highway without the fan. I have a new 4-core radiator, Edelbrock Victor water pump, Hi-flo t-stat, new hoses, and new intake/motor. In other words, the cooling system is better than original.

And please, if there's something wrong with my 'Vette, let me know!!!

 

Been running Clutch/fan for 25 years.Replaced original clutch(for fan) just two years ago. Have A/C. Never had a cooling issue driving mountains,deserts,traffic,etc.Highest temp once at 205 in 104 ambient outside air near Amboy,Ca. Just slowed down,and let fan "kick" in. 180 degree thermostat.Neat.

 

There's something wrong with your ' Vette. Thought you'd like to know.

My '73 has a LT1 spec engine in it and can sit in traffic all day long at 100 degrees outside temp without overheating. The gauge will go up to around 195-200 degrees, at which time you hear the fan clutch engage (audible fan noise) and then see the temp drop back to around 185-190. The cycle repeats until the car is in motion where the fan never engages again. This car has a stock '73 radiator, fan and fan clutch.

If you need a fan running full time to avoid overheating you have a problem, never mind pretending that running an electric fan 'saves power'