Recreating MP Viscous Fan Kit

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BrianT

BrianT

Here we go again...
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I am going to replace my 4 blade solid fan with a viscous fan. Since the MP performance kit is no longer available, I'm gonna try to do it myself. I know I can use the Derale fan clutch, but I need to find the correct 5 blade fan? I will also be buying a correct fan shroud. This is going on a 70 Duster 318 with Vintage Air.

Can anyone help point me to the correct fan? Thanks!

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The fan itself was a stock car fan but I don’t know which cars they came on. The latest offerings are a 6 blade fan.
FAN BLADES AND CLUTCH DRIVE UNITS

If you poke around enough, you’ll probably find the 5 blade fan.
 
Hayden makes all sorts of Fan clutches and on their website they have a great guide to all the specs of the clutches they offer.

I found a heavy duty 70’s Cadillac application that was bolt in and positioned the fan perfectly half way in the shroud on my ‘69 Dart 340.

Here’s some more info.

Fan clutch options
 
My 1990 W-150 w/318 has the 5 asymmetrical blades.
 
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i run a viscous that was cobbled together with junkyard parts. like said above the fan was nicked off a 80's FMJ so i'd probably start your search there.

interesting on the aluminum fan, i don't think i've ever seen one.
 
I'm thinking I heard the jeep wrangler runs the same fan as the vicious fan just different part number.
 
Hayden specifically made a short shaft fan clutch for our A body LA motor cars. I will post the part # tomorrow. Much better fit than the clutch unit in the MP kit.
 
The first thing to do is start with the original Mopar Performance part number. It is

P4120758.​

 
str12-340 said:
Hayden specifically made a short shaft fan clutch for our A body LA motor cars. I will post the part # tomorrow. Much better fit than the clutch unit in the MP kit.
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I have a new MP fan with the super short fan clutch I was going to use on my big block cuda.

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I have an original Viscous on my Dart which is an 18" one. The 80's-90's truck/van ones are 20" which is to big.
 
mopardude318 said:
There’s one on ebay right now.
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These fans are still out there. I’ve bought 2 over the last year. One came out of a van and cost me $10 and the other was from someone from this site or the B-bodies site. And be careful. Not all 5 blades are the same. It needs to come with a motor that uses a V-belt because a fan from a motor with a serpentine belt turns in the opposite direction I believe.
 
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mcodecuda said:
These fans are still out there. I’ve bought 2 over the last year. One came out of a van and cost me $10 and the other was from someone from this site or the B-bodies site. And be careful. Not all 5 blades are the same. It needs to come with a motor that uses a V-belt because a fan from a motor with a serpentine belt turns in the opposite direction I believe.
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Exactly right. the one I linked to eBay was the correct one. Looks like someone got it. Hope it was one of y’all!
 
Mancini sells a six blade and they say and I quote "This moves twice the air as Mopar P4120758" I gotta say, if you've ever had the 5 blade Mopar viscous fan, you know that statement is bs. They flat move the air and to move twice as much you'd hear it coming from a mile away. That's the benefit of the offset blades. They are quiet AND they move the crap out of some air. Mopar wasn't stupid. If the six blade fan was superior, they'd have used them.
 
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Richard Erinberg of Mopar Action had an excellent article but I don't know the issue #. You basically need the correct fan and clutch that dyno's about 15HP total loss. I forgot about the Engine Masters episode that tested many fans on a 440. They pulled somewhere from 50 HP down to the old heavy Mopar cluth fan at 15 or so! I run the set on my 512 work great, Just not real pretty as my other pile.
 
QuickDart360 said:
So how does the 5 blade compare to the 7 blade fan?
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Only thing conclusive that I’ve read is in the MP engine book regarding horsepower and torque: as it relates to new fans, 6 blades, symmetric, flex and plastic. No mention of cooling performance. Probably safe to say they went with the asymmetrical 5-blade for the best balance of power and cooling? I know I’d rather have a 17” version (I could probably cut a 1/2” off each blade on an 18” version...hmm) than the HEAVY 6-blade Derale I’m using.

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18" works good. I have one with a factory shroud and an aftermarket aluminum radiator. I had to use the short shaft clutch with this radiator.
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12many said:
Only thing conclusive that I’ve read is in the MP engine book regarding horsepower and torque: as it relates to new fans, 6 blades, symmetric, flex and plastic. No mention of cooling performance. Probably safe to say they went with the asymmetrical 5-blade for the best balance of power and cooling? I know I’d rather have a 17” version (I could probably cut a 1/2” off each blade on an 18” version...hmm) than the HEAVY 6-blade Derale I’m using.

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I would not cut a fan because there’s a chance that it might be out of balance. I still have a fear of fan blades after hearing a story of a guy that lost an arm when a fan blade flew off. It happened on a country road before cellphones were available so he applied a tourniquet and drove himself to the Emergency Room.
 
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