Wrapping my head around balancing

Magnum Engine Swaps

  1. pistolpete1934

    pistolpete1934 Member

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    Sorry for another post about balance but i have to get it right in my head... my build will be an 01 magnum 5.9. Stock cast crank, either stock rods or Scat's probably bushed for floating pins, Wiseco or JE forged pistons 30 over and whatever bearings the crank needs. As I am changing the weight of the internals and therefore require an internal balance, am I correct in thinking that I can use the dampener and serp pulley off of a 5.2 magnum as well as that engine's flex plate because that motor is internally balanced? Also use a neutral balance converter? I know all the pieces will have to go to machine shop for balance. Thanx
     
  2. Demonracer

    Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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    Balancing reduces the Total Harmonic Distortion, get with the machine shop & they can explain what pieces you need to bring in for balancing. After market pieces usually need less weight added or subtracted versus OEM parts because they are more closely scrutinized. I highly suggest balancing if you are turning higher RPM's because the higher you twist an engine, the higher the THD.
     
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    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      A stock 5.9 is NOT (factory) internally balanced!!! Are you saying this engine had previously been "built" and internally balanced by a machine shop? In either case, tho, changing ANY weight will change balane, AKA changing rods or pistons

      On the other hand just how wild is this thing? Many of those pistons may be designed for "stock like replacement" even though they are not necessarily same as factory weight. If this is a 6K/ under RPM street car you may be worrying about nothing.
       
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      • pistolpete1934

        pistolpete1934 Member

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        Nope, not saying it is internally balanced YET but assume it will need to be once i change pistons/rods. I guess i wont know what balancer or flex plate or converter it will need until i get everything over to the machine shop. It will be a mild build no more than 5600 rpm with street manners, roughly 26-2800 stall and a 3:55 gear. Not a race car by any means and i like it that way. Just want it to live a long life on the street and have some punch when I'm feeling playful...
         
      • 33IMP

        33IMP Well-Known Member

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        I think the stock cast cranks are intended to be externally balanced, the 4340 aftermarket forged cranks are intended for internal balance. The size and weight of the counterweights on the cranks are different. You can probably get your cast crank internally balanced, if the balance shop is good, but the mallory (heavy metal) necessary to balance it will probably triple the balance bill.
        Cheaper to use 5.9 accessories with external balance, than spend lots of money to internally balance just to use 318 parts.
        Lighter internal parts will make it easier to balance, because that means weight is removed from crank counterweights.
         
      • Bobzilla

        Bobzilla Well-Known Member

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        Your change of rods and pistons does not “require” internal balancing. Internal balance on this would require additional heavy metal added to the counterweights. That can be done if you want, and then you could use a 5.2 Magnum neutral dampener and flexplate, or any other appropriate neutral dampener and flex plate.
        As others stated, take your parts to see if it can be external balanced with the correct 5.9 Magnum parts.
        I have thought about this recently and I theorize it is likely possible to use LA 360 weighted dampener and LA 360 weighted flex plate and then balance it. I think this is how Mopar did their LA 360 replacement short blocks that used Magnum crank, Magnum rods, and LA 360 replacement pistons. I have verified the same casting number crank and rods were used in Late LA 360s and in Magnum 360s, but pistons were different and balance was different.
        Hope I am not rambling on too much again.
         
      • pistolpete1934

        pistolpete1934 Member

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        Not rambling at all. I have also read that the magnum pistons were the lightest they produced and would be a lightweight performance upgrade to the LA360.. quicker revving. Have you any thoughts on stock 360 rods small end bored and bushed for full floating pins?
         
      • pistolpete1934

        pistolpete1934 Member

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        Agree...
         
      • MoparLeo

        MoparLeo NRA PATRON LEVEL LIFE MEMBER FABO Gold Member

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        First things first. Find a competent machine shop. Check with them before you buy anything. They can recommend the parts that will complement each other and get the best value for your dollar. Pretty common for people to just buy parts that they read about and are disappointed when they don't get the performance that they were expecting because of a bad combination.
         
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