1. dust-u

    dust-u Well-Known Member

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    moving along on my 408 stroker build ... which damper would be best if i want to run stock pulleys?
     
  2. dano

    dano Evil Handy Man

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    • Early a body

      Early a body Well-Known Member

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      internal or external balance?
       
    • dust-u

      dust-u Well-Known Member

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      internal
       
    • dust-u

      dust-u Well-Known Member

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      builder wants to use ati damper but i cant see a provision for a pulley on it?
       
      Last edited: May 29, 2021
    • Plymouth 65

      Plymouth 65 Floorable Deplorable

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      You're builder obviously knows what he's talking about. I would only recommend an ATI Super Damper or a Fluid Damper. 65'
       
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      • 512Stroker

        512Stroker We are all here because we are not all there.

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        Street and/or strip?
        What rpm range will the engine operate at?
        Has the rotating assembly been already been balanced?
         
      • Heywodja

        Heywodja The Heartbeat Stops Here FABO Gold Member

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      • dust-u

        dust-u Well-Known Member

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        512... mostly street will see some revs north of 5500... everything balanced... i just want to use a balancer that will allow me to use my stock pulleys
         
      • 512Stroker

        512Stroker We are all here because we are not all there.

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        I would use a Fluidampr
        They work well across a broad rpm range and are very efficient.
        Contact them direct to check on pulley mounting.
        Chrysler Engine Harmonic Balancers • The Original Fluidampr
         
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        • yellow rose

          yellow rose Overnight Sensation

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          • Krooser

            Krooser Building Chinese Free Engines since 1959...

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            I have a Fluid Damper for my 388" bullet. It has been thru 30 nights on a dirt modified and is still good.

            Whatever the PO buys a damper is no place to go cheap...
             
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            • Nat

              Nat Well-Known Member

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            • 12many

              12many Well-Known Member

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              My experience with the Pro Sport was fine with a milder 410 for 3 years, but the outer ring managed to slip recently after upping the power via cam, heads etc. My experience is Possibly an outlier but it slipped nonetheless and I’m not using one again, the corrosion early on was a turnoff as well. Photos: Lined up together the Yellow mark on the oem balancer is “0” and the red line on the Pro Sport is “0” The timing markings are also about worthless without highlighting them as I did.

              2C035474-6078-4B9B-9E16-FE0CA41EC6D8.jpeg

              CE28328B-6B0E-40B2-B884-3E1C5A64C01F.jpeg
               
            • yellow rose

              yellow rose Overnight Sensation

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              Yours isn’t an outlier. Any time there is rubber in a damper it’s degrading from the first time it’s fired.

              The harder it’s worked (longer stroke, more RPM, heavier bob weight or all three) the quicker it loses its ability to absorb crank harmonics. It’s the nature of that type of damper. They generate huge amounts of heat. That heat breaks down the rubber, and that changes the frequencies that the damper can control.

              I’ve seen damper issues make bolts come loose, pushrod adjusters back off and all kinds of weird stuff. These cranks flex and twist a bunch. If that’s not accounted for bad things happen.
               
            • James Clews

              James Clews Well-Known Member

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              Do you guys know where I can get a fluid dampener for a small block? They all seem to be out of stock or something!
               
            • Nat

              Nat Well-Known Member

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              how do i know if it has slipped ? Don't want to find out the hard way so far there is no vibration , don't know how much HP you had or the crank pistons and rods you were using if it makes any difference . i'm using a molnar crank and molnar h beam rods with DSS forged pistons think the bobweight is 1800 . fuck i sure don't want that thing grenading at 7000 rpm , what should i get to replace this junk ?
               
            • 12many

              12many Well-Known Member

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              Only thing I can say with any of these type of balancers is to mark the ring and the hub prior to use (after verifying true TDC of course)
               
            • Bodyperson

              Bodyperson Pedal to the metal FABO Gold Member

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              • Plymouth 65

                Plymouth 65 Floorable Deplorable

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                Elastomer type dampers are tuned to a specific frequency. This frequency is determined by the 4th order on a V8 as that is the firing frequency. This frequency is the resonant frequency of the "system". Based on crankshaft stiffness and inertia, rotating and reciprocating inertia, piston / rod mass, and cylinder pressure through 720 degrees of rotation. This is modeled as a spring mass system for analysis and the cylinder pressure is used as the forcing function for the model. The problem is that most have no idea what the resonant frequency of the system is once you modify from stock components. Under tuned dampers will drive torsional amplitude higher into the engine operating range and can fatigue the crankshaft. Overturned dampers will drive the torsional amplitude into the lower engine operating range. A fluid damper is not tuned to a specific frequency. They work over a larger RPM range. The ATI damper is an elastomer damper but utilizes o rings that allow the inertia ring to slide within the casing causing friction damping. Friction damping has a high damping coefficient, and the sliding inertia ring will work over a larger frequency range. The o rings do require replacement periodically due to wear. 65'
                 
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                • Nat

                  Nat Well-Known Member

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                  Thanks i will give that a try , will mark inner and outer rings when the marks no longer line up i will know that the rubber has gone bad and it has slipped . i'll mark it in a few spots . you guys got me all paranoid now . in 40 years have never had a balancer gone bad , just lucky i guess . 8 years and 12,000 miles on my 340 with a made in china balancer and it has held plenty of over 7,000 rpm passes , i often forgot to shift into 3rd gear . when i built the 340 13 years ago i tossed the original balancer just to be safe went with the pro crap thought it was good obviously wrong . will buy the ATI THIS WEEK
                   
                • supertruck

                  supertruck Retired Old Fart stock car racer FABO Gold Member

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                  My 2 cents, and I've said it on other posts about this subject - go with ATI Super Damper. I ran one on my 4 cylinder mini-stock for many years. You know how those things vibrate. I turned that engine at a steady 5000 to 8000 RPM's all race, every race. We pull down the engine at the end of every season. Always see next to no wear on main and rod bearings, and the engine runs a LOT smoother throughout the RPM range. We've never had an engine failure. That's why I put one on the stout 340 I'm running in my 73 Sport.
                   
                • 512Stroker

                  512Stroker We are all here because we are not all there.

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                  Will the ATI work with your stock pulleys ?
                   
                • Nat

                  Nat Well-Known Member

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                  that is a good question , guess I'll find out soon . sure hope it fits , if not i'll sell it
                   
                • Nat

                  Nat Well-Known Member

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                  even with the pro crap dampner my 340 had zero wearonbearings everything was as good as new after 3 years and 7 or 8 thousand miles , but you guys got me paranoid now ATI IT IS
                   
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