360 la weighted flex plate do I need to rebalance?

Small Block Mopar Engine

  1. Josshh70

    Josshh70 Member

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    Hello guys, recently I had my crank balanced on my 360 la I had it balanced with an unweighted stock square style flex plate. Well come to find out the torque converter I ordered from PATC they forgot to put the butterfly weight on it, however I did order the proper torque converter for a 360la and I called and the guy said "well I wouldn't ever forget something like that". Sos here's my question should I have the crank re-balanced if I switch over to a b&m weighted flex plate or will I be okay running it the way the balanced it with the OEM flex plate?
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Define "balanced". Is this still yet an externally balanced engine, or did you have it modified for "neutral" balance. There is room for a lot of misinterpretation, here.

    EG If it's a "as stock" external balance engine, and you had a shop "balance the assembly" as such, it would have had to be balanced with the weighted balancer you are going to use, and the flywheel/ converter you are going to use, (or a weighted BM style flex plate for use with neutral converter)

    On the other hand if you had it modified --as with Mallory Metal, etc---to become a neutral balance engine, then you want all neutral components, ALL--balancer, converter, flywheel, flex plate etc
     
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    • Josshh70

      Josshh70 Member

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      I had them balance the assembly I got new rods, and Pistons. I had them balance those along with a new harmonic balancer and the OEM style square flex plate, he told me to stick with external balance as to add Mallory would be a fortune. So to answer your question in short I had him balance the assembly with the new rods, Pistons, harmonic balancer and OEM style flex plate.
       
    • Professor Fate

      Professor Fate Push the button, Max...

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      So, what you're saying is that your engine IS still externally balanced; and NOT internally (i.e. neutral) balanced, correct?
      Then you should be fine with the B&M 10239 flexplate (if using a 904) or 10236 (if using a 727).
      BTW, I would confirm with PATC (with pictures) that you actually do have a neutral balance convertor, and either get the correct one that you ordered or be compensated for your trouble; and not just give him a pass with "Well, I wouldn't ever forget something like that". That's BS. Would make me wonder what else didn't get done "quite right"...
       
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      • Josshh70

        Josshh70 Member

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        Yes my engine is still EXTERNALLY balanced. And I will be using a 46rh transmission behind the engine, and when I called PATC after the guy said I wouldn't miss something like that I then asked what could you guys do send me a shipping label and send it back to put the weight on or whatever. I also asked if maybe he put the weight elsewhere on the converter and he simply said nope if it's not on the front then there are no weights on it at all. He told me I could also ship it back but I would have to pay return shipping I live in MI and patc is in Louisiana, can't imagine the shipping on that. Or he said I could buy a b&m flex plate, really not much of any help IMHO.
         
      • PRH

        PRH Well-Known Member

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        I don’t know how you balance the crank for an externally balanced 360 with the stock neutral balance flex plate on it.

        It’s pretty simple though....... if the rear of the crank still requires the external weight........ and the converter doesn’t have it....... you’ll need the weighted flex plate.
         
        Last edited: Nov 16, 2021
      • Josshh70

        Josshh70 Member

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        I just didn't know if it would affect the balancing of the crank as they didn't balance it with the weighted flex plate, looks like I'll just order up a b&m flex plate and call it a day.
         
      • Professor Fate

        Professor Fate Push the button, Max...

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        • JDMopar

          JDMopar Well-Known Member

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          If a 46RH is the same as a 518, the above linked flex plate will work. There were never any weights added to flex plates on small blocks of the LA version. 5.9's, yes they had weights on the flex plate, but a 360 LA....NO. You're on the right track, so good luck with it. :)
           
        • Professor Fate

          Professor Fate Push the button, Max...

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          This is their screwup and not yours. If they won't pick up the tab for their mistake, I'd dispute the charge with your credit card company- you did not receive what you ordered.
           
        • Ahoey

          Ahoey Well-Known Member

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          When they balanced my first engine build in my dart it was an external balanced he used the stock harmonic balancer, one with counter weight and a B+M counter weighted flex plate as the B and M torque converter was not counter weighted. Engine ran very smooth. Second build used a scat forged steel assembly internal balance bought harmonic balancer from scat had machine shop cut counter weight off flex plate in lathe and neutral balance it. Assembled it and it run real smooth. The difference in bob weight from stock with trw 12.5 pistons to scat rotating assembly with icon 10.5 pistons is almost unbelievable almost a lb. very happy with scat’s products and service
           
        • IQ52

          IQ52 Well-Known Member

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          "well I wouldn't ever forget something like that"
          So you ask the guy who balanced the engine what flex plate and converter to use to go with his balance. Everybody else is just guessing what you need.
           
        • Ahoey

          Ahoey Well-Known Member

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          TRUE. Believe the man
           
        • PRH

          PRH Well-Known Member

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          This is my point.......
          You can’t balance a crank that requires external weight...... without the weight.

          The weight is part of the balance.
           
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          • IQ52

            IQ52 Well-Known Member

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            How much valve spring pressure should I use on my cylinder heads. I don't know what cam the installer used but he said didn't forget to time the camshaft.
             
          • 70aarcuda

            70aarcuda Master Hoader of SBM FABO Gold Member

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            Did he provide you with a print out on the balancing of the engine?
             
          • Ahoey

            Ahoey Well-Known Member

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            Can shaft timeing is done by key ways in cam gearing and machined dots on gears plus or minus your split key
             
          • IQ52

            IQ52 Well-Known Member

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            Good Lord. Will I ever learn to just be quiet?
             
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