Is anyone using a Viscous Fan?

[charger1970]

I was thinking about getting a viscous fan for my 383. For the people who have switched to one, is there much of a performance difference?

[451Mopar]

Short answer; it works good, sits a bit closer to radiator, performance gain unknown.

[tsteiner61]

The viscous fan is really just a regular fan with a bimetal thermostatic clutch device and one less fin. When underhood air is cool, the fan turns slower, thus theroetically requiring less hp to run the belt. MPP says up to a 15 hp difference, but I don't buy that. I would say 5 hp, and that's only when the underhood temp is cool. If the underhood air temp is hot, this fan acts just like the fan you have now, no gain. If you can fit one and afford one, go with an electric fan setup. That way you know you get an hp gain over stock at all rpms and conditions.

[timty2]

The theory on having the fan "Slip" at higher engine speeds sounds good to me... Without going to electric fans, this seems to be a good setup. My experience is they work well, but make sure your fan shroud is in good shape and not warped.

Man, I wish I had a dyno to collect the data on fan only upgrades. Do a Stock fan VS Viscous VS Flex VS Electric VS No fan comparison... get some hard HP data on fan only upgrades.

Electrical fans are not "Free" though! I'm sure they have their HP losses too. Just puts more load on the alternator.

The Mopar Viscous Fan Package has a stock type fan, with uneven fan blades (Three on one side, closer together and 2 on the other side, farther apart.) I guess the theroy is better cooling is achieved by "Pulsing" the air through the radiator than a more even flow? Anyone know more about this?

[6 packin]

Confused!

If the under hood temp was cooler I under stand that the fan would turn slower, but I would think the coolere air would result to the perf gain right. Cold air is more dense (more Oxygen)

[tsteiner61]

Very true...

Cooler underhood air will always result in a perf. gain, however, I think you get an additional benefit due to less load on the fan belt translating into some additional hp.

[charger1970]

Does anyone know what kind of HP gain there is from an electric fan?

[Mills]

Take the belt off the fan for a SHORT blast....you will feel the difference w/o the fan being driven by the engine. I used to take off all the belts with my old 318 poly to race - I would get beat by my friends '96 DAK w/ 318 by 3-4 lengths with them on, after taking them off - I beat him by 3-4 lengths.

Now I run a 8 blade HD fan off a cop car w/ viscous drive - It works good. And I couldn't stand that B747 sound the "solid" fan made.

[Larry S.]

That B747 sound is the reason the clutch fans have the blades spaced out in an oddball pattern, it keeps the harmonics down. If you look at the tread on your street tires you'll notice that the tread blocks squeez together and spread apart as you go around the tire, same principle, it keeps the whine down on the road.

[rumblefish360]

I made the switch from the stock 8 blade to the viscous unit. There is a big wind diff. under the hood. It ran cooler right away. That 10-15 hp diff. is secne in performance cars over the stock fan.
Car craft did a fan shoot out some time back. Bottom line is the electric made the most HP. The extra load on the ALT. is moot. It's turning anyway.

[440cj]

I agree with Rumblefish, the article he mentions stated the electric gained 27 hp over the flexfan that was first used, the next closest was the clutch fan which gained 21 hp over the flex unit. I always have used the clutch fan...no problems and no overheating. 440cj

[George G. Leverette]

Some other factors to consider. The fan comes in 18" or 20" diameters with 5 or 7 blades. The viscous fan clutch comes with or without thermostatic control and there is a long neck and short neck mounting to get the correct distance from the radiator. The 5 blade 20" fans are plentiful in the yards for about $10.00 the clutch is about $50.00 with temperature control. Recommend you measure the one you have now and try to duplicate the correct size and neck length.

[charger1970]

When they were doing there testing what engine were they testing on?