Which one flows better, factory 6 blade water pump or 8 blade

Heating / Cooling / AC

  1. 340doc

    340doc Well-Known Member

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    I'm aware the so called A.C. pump has 6 blades while the non A.C. has 8. It would seem the 8 would move more water hence a cooler running engine. Seems like the air cars would need the better flowing unit. Also the Mopar bible recommends the A.C pump for a HP build, stating less drag. What gives?
     
  2. Johnny Dart

    Johnny Dart Well-Known Member

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    AC cars have a smaller pulley, which spins the 6 blade water pump more turns per cycle. Using an AC pump for a HP build might be less drag, but at the expense of cooling. If you are going one quarter mile at a time, cooling is less of a factor.
    I would stick with the way the factory designed the pumps in AC and Non AC cars.
     
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    • 340doc

      340doc Well-Known Member

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      Ok, pulley size makes sense, thanks.
       
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      • MOPAROFFICIAL

        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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        Here's the deal with the water pumps. Cars with lots of accessories like AC got the 8 blade water pump because those engines were dragged down and got a little warmer running all those accessories at idle. Mopar performance recommends use six blade simply because there's less drag and they don't expect you'll be idling much. If you have a hot Street motor strip motor and you're driving around town you're really going to want the 8 blade pump because if you do any kind of sitting in traffic drive-thru your motor is going to get a little warmer than norm.
        The other thing to consider is that Mopar and they're testing came up with an idea that the eight blade might cavitate at really high RPM. I run the eight blade myself and have no issues running it at high RPM ...and you really don't stay up there long , so it's not an issue. That was more of a racing thing.

        Six blade, I have no use for them.
        8 blade for street strip.
        Add the anti cavitation plate version for constant high rpm..or buy the milodon,jegs,flowcooler.. etc version.
        And a caveat to that is you can run a 6 Blade with a plate and probably push about as much water as a regular 8 blade.


        You can do it a couple different ways.

        Parts store 8 blade-cheapest.
        Jegs 6 blade w/anti cavitation plate-70.00 iirr.
        Milodon and the rest are the more $$.

        All you need.. is what works.
        Mostly is lack of enough low rpm clooant flow that's the issue.
         
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        • ir3333

          ir3333 Well-Known Member

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          Johnny Dart is correct.The pulleys were sized to move the same amount of water.Stick to factory specs.
           
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          • MOPAROFFICIAL

            MOPAROFFICIAL FABO Gold Member FABO Gold Member

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            Then you're saying to the guy you MUST run a zillion groove ac pulley.
            No thanks!
            We are NOT restoring to stock, so that's irrelevant what pulley the factory used!
            Johnny is just giving you a history lesson more or less.

            Use the non a/c pulley, be it with or without power steering and the 8 blade pump. It works.
             
            Last edited: May 20, 2020
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            • 340doc

              340doc Well-Known Member

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              Thanks for the detailed explanation.
               
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              • ir3333

                ir3333 Well-Known Member

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                Stock mopar water pumps flow 20 % more than Ford or Chev. No need to try and increase the flow...you won't gain anything but cavitation.When the engine reaches thermostat opening temperature it will open and the stock pump will be more than enough.
                But you can change pumps and pulleys if you like to try things.
                 
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                • rumblefish360

                  rumblefish360 So close, yet so far away FABO Gold Member

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                  When it comes to cooling the hot rod, factory stock has never let me down. Shroud, 18.5 viscous fan, pulley sizes, it’s all good stuff. It handles a little racing. Just a 1/4 or so in the back alleys at a time. On the track it’s nothing.

                  I’ve had both 6 & 8 blades on the car and noticed nothing. The SB engine was in the 450 HP area.
                   
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                  • QuickDart360

                    QuickDart360 Well-Known Member

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                    I went with an 8 blade mopar pump in my 360. May try a 6 blade at some point. I have an 8 blade clutch fan. I wonder if a five blade mopar performance version is as good or cools less?
                     
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                    • pishta

                      pishta I know I'm right....

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                      Davies-Craig EWP and fan controller on a Meziere electric water pump. For those who have everything....dont even need a stat...

                      shopping.jpeg
                       
                    • Johnny Dart

                      Johnny Dart Well-Known Member

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                      I'm only talking about the water pump pulley and water pumps. Never did I say anything about crank pulleys.

                      Fact:
                      AC cars: 6 blade water pump, small water pump pulley.
                      Non AC cars: 8 blade water pump, bigger water pump pulley.
                      Only 1 of my cars has AC. It has the 6 blade setup.
                      The non a.c. car has the 8 blade setup.
                       
                      Last edited: May 20, 2020
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                      • MOPAROFFICIAL

                        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                        Good, neither did I.

                        Fact. They put both behind both depending on the app. I've torn apart more cars, trucks, Van's than I could even count.

                        Pop quiz
                        ..The impeller shaft is bigger on one pump than the other, which is it?
                        Thanks for playing.
                         
                      • MOPAROFFICIAL

                        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                        5 blade clutch, Tried it, for me it sucked.
                        I'll never run that heavy pos again Jkn.
                        It didn't move enough air.
                        But I really have no desire to fund out because i have what works already.

                        The right capacity and adequate low speed cooling fan, winner every time.
                         
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                        • Johnny Dart

                          Johnny Dart Well-Known Member

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                          Nothing to get upset about.

                          I was assuming when you said "zillion groove AC pulley" you were talking about the crank pulley ?
                           
                        • MOPAROFFICIAL

                          MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                          Not at all.
                          Water pump pulleys came/come with more than one groove as well, depending on motor and car...but I get why 'zillion groove' =crank pulley. Neat when they have been bent slightly...and they just lightly wobble on the nose of the crank at idle. Looks so shitty.
                          I'm out, I offered my 2cents on water pumps.
                           
                          Last edited: May 20, 2020
                        • famous bob

                          famous bob mopar misfit FABO Gold Member

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                          I always wondered and thot about people saying to use the factory 5 blade fan , I dont see how it could move as much air as more blades , best I remember , it was for fan noise only.
                           
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                          • Demonic

                            Demonic Well-Known Member

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                            I've found that the regular thermostats are the biggest restriction in Mopar cooling systems.
                             
                          • MOPAROFFICIAL

                            MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                            I will admit I have been running mr.gasket high flow for the last 20yrs.
                            Same one!!
                            Highly recommend them. 165,185,195 degree ratings made of brass.
                             
                          • AJ/FormS

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

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                            My 2 cents;
                            From a streeter's point
                            I run a minimum coolant temp of 205*; that's the job of the hi-flow stat.
                            If/when the gauge starts climbing, I want to know why right away. So I built my system overkill so that when I raise the rpm at zero mph, instantly I see the temp drop. That way I have peace of mind.
                            Overkill:
                            >8-blade plated pump with the big shaft.
                            >As many blades as you can get; I run a 7-blade all-steel, hi-attack fan with the curved up tips.
                            >molded hoses with the anti-collapse spring in the suction side.
                            >a restricted bypass circuit; I use the heater as my bypass, until the summer weather warms up,lol..
                            > a shroud, and a core-support seal, with rad sealed to the sheetmetal
                            > For my 400hp 367, I use an ancient 1973 rad that came out of a smoggerteen Dart with A/C
                            > Straight Water is a way better coolant than 50/50 Ethylene Glycol; but I am forced by climate to run the 50/50.
                            > don't forget; fresh cold air into the carb. If you force your carb to process air at 300plus degrees, well, good luck with your nuclear reactor.
                            > to make it all work automatically, I installed a HD thermostatically controlled clutch, off an early 2000s Ford pick-up truck.

                            Now; before you yell powerloss!, think about it. As soon as your car hits about 35 mph, your radiator will be ram-air cooled and the clutch will freewheel. Forget any Magazine's fan-test!
                            Ok sure, below 35 mph, when that 7 blade kicks in @100%, it will stall your 273.(That's a poke). But it never does kick in @100% on mine, and I hardly ever notice it ( manual trans car). The thing is, whats more important; your mega-buck engine's life, or 5 hp@35mph, whenever the clutch kicks in? Hmmm?
                            My engine gets additional cooling from;
                            Fresh cold air to the carb,
                            the 7Qt oilpan,
                            aluminum heads,
                            AirGap intake,
                            camshaft EGR,and
                            the full length dual 3" exhaust pipes, with un-wrapped, and un-coated, headers.
                            I didn't mention the WP drive ratio, because contrary to popular practice, mine is underdriven, to give the stinking belt a fighting chance at staying in the grooves at 7200rpm.
                             
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