5 blade vs 7 blade clutch fan

Heating / Cooling / AC

  1. mopardude318

    mopardude318 Well-Known Member

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    What are the differences in cooling capability between the MP 5 blade viscous fan and this one I have here, which is a 7 blade unit, but I don't know what it came off of? Big block? Motorhome? Max cool package?

    I'd like to use either of these on my 408 stroker, but what is the max rpm for these, considering the clutch will be replaced with a new one. :) it sure seems like this 7 blade unit can move a huge amount of air.

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  2. rumblefish360

    rumblefish360 so close yet so far away

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    If you have the off set 5 blade fan, that was a MP viscous unit MP used as the best to move air and cool the radiator/engine.

    I never heard of a rpm limit to them.
     
  3. brian6pac

    brian6pac Well-Known Member

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    I would keep the 7 blade aluminum fan, it will move plenty of air, Plus it's aluminum!
     
  4. TrailBeast

    TrailBeast Slightly Twisted Member

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    That's because any possible witnesses to the limit were all killed when it came apart.:D
     
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    • rumblefish360

      rumblefish360 so close yet so far away

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      It makes sense that more blades move more air but that actually may not be the case. I personally don’t know. But it makes me wonder, if such was the case, then why didn’t MP have it for sale and suggested use in the catholic and books.

      There may be something to that weird 5 blade off set fan. Who knows? All I can say is when I swapped fans to help cool my engine, ther was a huge difference between the stock one and the MP viscous fan by Hurricane standards!
       
    • Ernie B

      Ernie B Well-Known Member

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    • Ernie B

      Ernie B Well-Known Member

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      I have a 7 blade clutch fan in my duster with a 429 stroker with AC, runs cool on hottest days with AC on. The 7 blade fan was a police car fan.
       
    • Murray

      Murray FABO Gold Member FABO Gold Member

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      Please correct me but it seems to me that seven bladers and seven bladers w/ fluid drive were more of a BB thing- like an Imperial w/ air conditioning. Don't remember any seven blades on a small block.
       
    • 68 Coronet RT

      68 Coronet RT 68 GTS # 508 in Registry

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      I went from a 6 blade 17" to a 7 blade 18" and it made a huge difference. Temp dropped 10 degrees and I still have a bad radiator. Waiting for my new direct fit radiator from Cold Case, hopefully will be here in a few weeks.
       
    • rumblefish360

      rumblefish360 so close yet so far away

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      Press reply, wait a few seconds, type on ether side hey f the quote tags. ;)
       
    • oldkimmer

      oldkimmer FABO Gold Member FABO Gold Member

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      My 70 swinger 340 and duster/ demon 340s all came with a 7 blade viscous fan. The clutch part was actually a de clutching unit. Kin
       
    • ir3333

      ir3333 Well-Known Member

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      the pitch of the blade also determines air flow.
       
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      • MoparMike1974

        MoparMike1974 Well-Known Member

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        My 73 340 has 7 blade. Its part of the "max cool" package.
         
      • famous bob

        famous bob mopar misfit

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        Originally, the screwy offset blades were made so they wouldn`t make as much noise.
         
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        • BillGrissom

          BillGrissom Well-Known Member

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          Ditto. The nylon clutch fan in my 1985 M-B has offset blades. I don't recall how many, but at least 7 and much thinner than Mopar fans. Some use those in a Mopar because they are ~1" less thick. Slant engines are most pressed for space. Jaguar fans are similar. Both bolt up to the Mopar water pump (same bolt pattern and hole for the shaft). Some other car apparently has the same bolt pattern but a thicker w.p. shaft since I once got a Mopar fan clutch that came w/ a spacer needed to make the hole fit my Mopar. Probably not Chevy since I recall those use 3 bolts (cheap bastards), so perhaps Ford.
           
        • scatpackbee

          scatpackbee Well-Known Member

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          Please post your thoughts and findings on the Cold Case radiator install.

          Is your Dart a 340 with the drivers side rad inlet and outlet?
           
        • RustyRatRod

          RustyRatRod 30 Degrees Outta Whack FABO Gold Member

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          Actually, rumblefish is right. The 5 blade offset fan was made for two purposes. First, it moves more air than the symmetrical 7 blade fan. That's why it was sold as part of the performance package in the Direct Connection and MP catalogs. And yes, a side benefit to the offset blades is that they made less noise. But not by much.
           
        • 68 Coronet RT

          68 Coronet RT 68 GTS # 508 in Registry

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          scatpactbee, still waiting for the radiator. I talked to Chris from cold case radiator a couple of weeks ago and they have been extremely busy with current products and it set new product development back a few weeks. I will be talking to Chris towards the end of the month for a update, I do not want to keep bugging him when it's done I will be the first to have one and I will let everyone know how it fits. Yes mine is a 340 with both inlet and outlet on the driver side. The car been down for the last 3 weeks with a bad steering box. Just got a replacement box from Steer and Gear out of Ohio this week and finally got it installed. I wouldn't wish that on anyone what a PITA to replace that box, mine is a power steering box.
           
        • scatpackbee

          scatpackbee Well-Known Member

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          I had a power steering box rebuilt by Steer and Gear (stage 3) last winter and installed it this spring. I know what a pain in the butt it is to install.

          I purchased a Cold Case rad this past June when I was on the HOTROD Power Tour as they were a vendor at the destination venue on the tour.

          I bought the rad as a "back up" because I my Dart was running pretty hot in stop and go traffic with the A/C on, but I managed to get through the tour with my factory rad after I swapped out the Hayden thermostatic clutch with the factory torque clutch which dropped my temperature at idle.

          I bought the MOP751A "bolt in" radiator for a '69 Dart small block with cast iron water pump, but noticed the coolant inlet fitting is more inboard than the factory rad by around 1.5 inches I think, which for me will be a problem because the rad hose would now hit my A/C compressor. It also appears that the outlet port is also off from the factory rad. I also don't think that the factory shroud will bolt up despite them telling me it will. I still haven't tried to install it yet.

          What is different with the rad your getting? Did they correct these issues I see with mine?
           
        • YY1

          YY1 Well-Known Member

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          Two comments-

          The offset blade also allow room to get a hand and wrench in to install the fan and other things.
          You absolutely could not work on the front end of my Dakota without the offset.

          Not sure about automotive fans but statistically, a four blade home ceiling fan moves more air than a five blade fan. Sounds non-intuitive, but it's true.

          IIRC the same applies to impeller blades n water pumps- the high capacity ones have fewer blades.
           
        • 68 Coronet RT

          68 Coronet RT 68 GTS # 508 in Registry

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          Yes they corrected the issue, I was talking to Chris about a week before the Syracuse Nationals he told me he was going to be here in Syracuse, Chris said he would bring the 2 rads that he thought would work plus they were the ones I saw on their web site that I thought would work. Not close I would have to modify them to fit. I took all the measurements off my rad with me when I went over to see Chris at the Nationals and compared them. I would of had to really modify them to fit. Long story short I went home got my original rad from my Dart and took it over to Chris on Sunday and he took it back with him to use as a template to build a direct fit radiator for the A bodies. About 4 weeks later I got my original rad back. They took all the required measurements to build a direct fit 2 row 1 1/4 tube rad including the ability to use the factory shroud, which his current rads do not have the ability to use a factory shroud. When we compared his current rads next to mine he saw the big difference to where the inlet and outlets were located, so that's where we stand right now, hopefully within a few more weeks I will have it. I plan on making a video of the installation and putting it on youtube. Chris is really a great guy to deal with, he is very knowledgeable about his products and how they perform. I would never have a issue doing business with him and Cold Case.

          I went with what Steer and Gear call their Modern Feel on my new box, they told me that's pretty much what everyone orders now. They said nobody orders the factory feel, I can see why for sure.
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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          I tried several different factory fans between 99 and 2000,including flex-fans, smaller 6-blades and the large Mopar 5-blade/ viscous drive.
          Nothing did the job until I installed the 7-blade.
          That 7-blader has made thousands if trips to 7000/7200,slightly underdriven, since ~2000, the T-clutch went on in about 2002, after the viscous couldn't keep up; same year the Hi-flow pump and stat went in.
          That 7-blade was already 27years old when I installed it, being a 1973 model.
          The only time I hear it is when it cuts in at idle, and I am standing outside the car. My rad is also a 1973 A/C model, off a 318-Dart.
          Not a stroker, just a 367HO.
           
        • scatpackbee

          scatpackbee Well-Known Member

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          Do you have a contact email for Chris at Cold Case?

          I would like to contact him regarding the fitment concerns with my brand new rad.
           
        • 68 Coronet RT

          68 Coronet RT 68 GTS # 508 in Registry

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          scatpackbee
          I finally just got a email from Brian this afternoon from Cold Case Radiator, Brian is the manufacturing manager at cold case. The radiator will be finished next week and once it goes through QC it will be on it's way to me. Once I get my hands on it I will let you know. I plan on taking many photos and a video of the installation. Been doing some work on the car, still can't stop that tranny line from seeping so I ordered a new set of lines. I do have some parts for sale, I'm selling a Edelbrock 750 performer manual choke carb that was rebuilt by National Carburetor out of Jacksonville Florida they are simply the best around. It's still in the original box it came in and it's never been on a car $200.00 US. I'm also selling 2 BFGoodrich 245/60/15's T/A Radials with less than 700 miles on them, I have decided to go with a taller tire, $225 US. Going to take the 3:91's out and put 3:55's in, so I will be selling the 3:91's and also the set of 3:23's probably $175 for each set. The 3:91's are a Richmond gear with less than 700 miles on them. They are for the 8 3/4 489 case. If you should happen to know anyone looking please let them know.
          Won't be long now
          Lenny B
           
        • scatpackbee

          scatpackbee Well-Known Member

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          Great news!

          Please let us know how it fits.
           
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