ATI super damper?

Big Block A body Tech

  1. Craig Burriss

    Craig Burriss Well-Known Member

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    Hey guys, I’ve been considering getting an ATI super damper for my 440 for a while now. Are they worth it?
    When my 440 reaches about 3500-4000rpm, I feel a terrible vibration in the whole car.
    It’s got a stock crank and rods with aluminum pistons, custom flywheel for my crankshaft, GM style clutch, and a summit racing brand balancer that’s only a few years old. I’m using modified RamCharger polyurethane motor mounts, with a chain to keep them from ripping apart.
    Thanks
     
  2. 80fbody

    80fbody Well-Known Member

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    Gonna say part mismatch with respect to balancing and doubt a $400 ATI damper is gonna solve it unless you have the wrong balancer for your application.
     
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    • pishta

      pishta I know I'm right....

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      the 'balancer' in this app (custom parts) must be neutral, only a damper for harmonics, Has none to do with the internal balance of a motor as crank had to be balanced to the crank/rods/pistons prior to installing the neutral balancer UNLESS the balancer was a cast crank model with the eccentric weight. IIRC you cannot balance a motor with any balancer attached, especially a fluidamper. I dont think there is a way to get it balanced without checking for a thrown convertor weight or bad U-joint. Then its balance time again.....That sucks.
      << remove all the belts and see if it still vibrates at your range to remove doubt of a bad fan>>
       
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      • PRH

        PRH Well-Known Member

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        Why did the motor need a “custom” flywheel?

        I agree with the mismatched parts theory.

        Do you know for certain if the motor has a forged steel crank or cast crank?
         
      • Craig Burriss

        Craig Burriss Well-Known Member

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        The flywheel came with a T56 magnum trans kit.
        I have a cast crank
         
      • TT5.9mag

        TT5.9mag Two atmospheres are better than one

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        Sounds to me like you have a couple pieces of the puzzle mixed up. Your flywheel is likely neutral balanced, your damper (I assume stock) is for an external balance crank so it’s weighted, and your rotating assembly is externally balanced but wrong because you changed pistons. Was this whole bottom end balanced as a unit when the engine was built? If not it needs to be. A new expensive balancer will not fix it.
         
      • DC Dart

        DC Dart Active Member

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        Could be neutral balanced flywheel on external balance engine. Should be able to look at previous flywheel and see if it was external or neutral balance. Cast was external I believe. Wrong weighted flywheel will cause harsh vibration.
         
      • Craig Burriss

        Craig Burriss Well-Known Member

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        The engine was not rebalanced, but all of the rods went back into their original holes with the new pistons. I have the transmission out of the car right now for a throw out bearing, so I’ll have to look at the flywheel. The engine was originally attached to an automatic, so no old flywheel to look at.
         
      • pishta

        pishta I know I'm right....

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        were the pistons replacement pistons (ie Badger that weigh the same as stock) or Probe/Icon/KB/? lighter/heavier ones? if they were not the same weight as the ones that came out, then there is one possible cause. If you can take a piston out and weight it and compare it to published weights of a stock piston for that year 440 (69 forged crank 440 piston/pin weighs ~1086g) , then maybe youll get some good data.
         
      • PRH

        PRH Well-Known Member

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        As has been mentioned, if the replacement pistons are any kind of “performance” piston, they would be lighter enough than stock to warrant getting the crank balanced.
        With external balanced rotating assemblies, the damper and flywheel need to be installed during the balancing process.

        What I did to make up some external balance flywheels to use on the dyno was to duplicate the amount of imbalance from a B&M weighted flexplate onto a std zero balance flywheel.

        So, if your flywheel is zero balance, that’s one way to get you “closer” to being correct(have it matched to the correct B&M flexplate).

        There are also some old drilling diagrams in the MP manuals that tell you where to drill a std flywheel for use with an external balance crank.
         
        Last edited: Aug 26, 2021
      • PRH

        PRH Well-Known Member

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        This is how far off the flywheel for an external balance 440 crank is:

        2000AFE4-EFA1-45B8-811C-2522C024C3CF.jpeg
         
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        • Craig Burriss

          Craig Burriss Well-Known Member

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          They’re speedpro aluminum pistons.
          I’m planning on eventually putting this 440 in my RamCharger so until I’m not going to tear into it,
          So just so I understand, the cast cranks of 1977 were originally externally balanced via flexplate/flywheel?
           
        • TT5.9mag

          TT5.9mag Two atmospheres are better than one

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          Cast cranks of any vintage are balanced by weight hanging off the front and the rear. Usually on the balancer or flywheel/flexplate or converter and any combination of those things. But even if you get all of that correct for the engine, the balance will still be off because you changed the bob weight by substituting lighter than stock pistons.
           
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          • PRH

            PRH Well-Known Member

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            All cast crank 440’s are externally balanced on both ends.
            All use a weighted damper on the front.
            Std trans applications used a weighted flywheel.
            Auto trans applications used a weighted torque converter.

            My guess is your issue is that you likely have a neutral balance flywheel bolted to the motor, creating a significant “out of balance” condition.
             
            Last edited: Aug 26, 2021
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            • PRH

              PRH Well-Known Member

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              I believe all the Speed Pro flat top pistons would be pretty close in weight to factory pistons.

              If that vehicle has an auto trans, I’d suggest buying the correct B&M weighted flexplate for the cast crank 440, and pair it up with a neutral balance converter.

              B&M 10237 B&M Flexplates | Summit Racing
               
              Last edited: Aug 26, 2021
            • pishta

              pishta I know I'm right....

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              lighter pistons may allow you to internally balance that thing and then (buy) neutral balance everything else (ie Superdamper is neutral) cast cranks were lighter than forged so they had to add material to have them balance to the same production rods and pistons so they had to add weight to the damper and flex/flywheel. Now that you have possibly lighter pistons, that may be closer to the natural bobweight of the cast crank and your externally balanced parts (cast crank balancer and flex/flywheel/convertor) would be not needed but it would have to be disassembled and weighed, then balanced anyway. If you buy neutral components (convertor/flexplate/damper) and have your crank internally balanced your good to go in the future.
               
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              • pishta

                pishta I know I'm right....

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                If thats the case, then its probably that custom flywheel that wasnt balanced to the external balance specs of a cast crank 440. That's about the easiest option he has, remove the flywheel and have it balanced to a stock cast 440 flywheel spec like this one
                dcp_0038-jpg.jpg
                Somewhere there is a weight kit for a convertor but it may have the balance specs for this operation
                Mopar Performance P4120241 Mopar Performance Balance and Positioning Template Packages | Summit Racing
                 
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                • Machineman63

                  Machineman63 Well-Known Member

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                  Balancing.
                  one gram of out of balance at 2k RPM squares at 4k RPM and that again at 6K
                  spend your money wisely when building an engine, factory balance wasn't even close.
                   
                • Craig Burriss

                  Craig Burriss Well-Known Member

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                  Got the new weighted balancer installed. I’m amazed at how smooth the engine runs now. It’s like a new car!
                  Thanks guys.
                   
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