Internally Balanced 360 Cast Crank

Discussion in 'Small Block Mopar Engine' started by 70aarcuda, Apr 20, 2017.

  1. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    Just picked up Internally Balance 360 Cast Crank today. The crank was balanced with SRP 360 .040 pistons. Scat I beams rods. Weights are shown on the worksheet. The crank still took one slug of Mallory in the front and rear counterweights.

    Attached is the worksheet I think, scanner at work does not want to work for me tonight so I took a picture of it. Will scan to pdf sometime tomorrow after MATS.

    20170420_214334_resized.jpg
     
  2. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    SRP 142070 flat tops 505 grams
    Rods small ends 167.10 grams
    pins 137.7 grams
    locks 4.7 grams
    rings 48.40 grams
    Reciprocating WT 1725.80 grams
    Half BobWT 900 grams

    rod big end 417 grams
    bearing 49.3
    total 466.30 x2
    937.10
    bobweight 1800

    Reciprocating % 50....Reciprocating Factor 862.90
     
  3. j par

    j par Well-hung Member

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    As I recall my machine shop had a similar situation with mine. Cast scat internally balanced 4" with scat I beams .040 over -anyways, lot$ of mallory. I remember the stuff being not cheap.
     
  4. 2fine69s

    2fine69s 69 340-6pak Rag Top FABO Gold Member

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    I ran the same, years ago and the machine shop put the mallory in the end of the throw and not the side. The first time i turned it up, it slung the mallory thru 7-8 cylinder. Built another with the mallory in the side of the throw, used a 575/308 comp solid roller, 11to1 KB pistons. Would run 7.90's every pass with a 7" wide tire, full body Dart.
     
  5. nm9stheham

    nm9stheham Well-Known Member

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    Thanks for the data, and your sharing is very much appreciated. (My Excel sheet spits out the exact same bobweight...) That is about as light a batch of parts as I know to use.

    Can the shop tell you how many grams of equivalent weight was added at each end with the Mallory, and at what distance from the crank centerline? That would be VERY useful to know.

    The only other trick I know is to counterbore the front and rear throws, like in the 340 forged cranks, and see how far that gets you. Or notch the pan rails a bit and see how much extra can be welded on the outer edge of the counterweights.
     
  6. dusterdoug

    dusterdoug Well-Known Member

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    Makes me wonder if an internally balanced forged crank is cheaper in the long run...
     
  7. yellow rose

    yellow rose Doctor of Thinkology.

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    They can tell you if the know how big the slug was. I used to have a chart that showed the weight of tungsten but I can't find it.

    A 1x1 slug of Mallory would weigh X amount, minus the material revved from the crank gives you the net gain.

    It may have been a .750 slug I was using that as an example.
     
  8. yellow rose

    yellow rose Doctor of Thinkology.

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    Yes, a thousand times yes. A forged crank is always cheaper in the long run. I would not sell a cast crank to a guy who wanted it internally balanced. They either got it externally balanced, bought a forged crank, or went to the shyster down the road.


    I will never, even if I live to be Methusala age will I ever understand the irrational behavior of stepping over donuts to pick up dog turds.
     
  9. dusterdoug

    dusterdoug Well-Known Member

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    Well I was speaking in terms of a guy needing to buy a crank. Obviously, if you already own a cast crank, that $300-ish balance job is cheaper than a $750-800 forged crank.

    So let's go down the cat crank road for a minute: I have never had a cast crank rotating assembly balanced, but just might soon.

    That said, what is the safe RPM for externally balancing of a 360 do y'all think??
     
  10. nm9stheham

    nm9stheham Well-Known Member

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    Yes sir, that is all correct. I can compute it all out. But I don't know how big the slugs are or any other adjustment. I was hoping that 70aarcuda was given that info; I'd like to know how close it was to start with.
     
  11. yellow rose

    yellow rose Doctor of Thinkology.

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    So why piss away $300.00 for an internal balance when you don't need it? If you want it internal, buy a forged crank.


    BTW, I don't know who is doing your machine work, but they are either double damn good, or he works way too cheap. $300.00 wouldn't get you a balance job with Mallory. It would start at double that, and go up from there and would depend on how long it took, with another $50.00 just because it's such a pain in the ass to do it.
     
  12. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    After things slow down for a few days I will check on those items..for who wants to know..the balance job including the mallory was 400 bucks.
     
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    • 70aarcuda

      70aarcuda Master Hoader of SBM FABO Gold Member

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      It is my money so dont lose any sleep over it...

      And look beyond the cost of the balance job...dont have to buy new SFI externally balancer.....already have neutral sfi balancer...dont have to buy sfi weighted flexplate...already have sfi neutral flexplate....add those to the equation...maybe the light will come on
       
      Last edited: Apr 21, 2017
    • yellow rose

      yellow rose Doctor of Thinkology.

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      You move from the ASSumption that you had all the internal stuff to start with.


      Most of the time, (I'm very pragmatic, and understand reality) most guys already have the EXTERNAL shit, and they pay to make it all internal.


      As a wise southern guy once said...it's your goat, hump it how you want to.

      Maybe you need to exercise your inner pragmatic?
       
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      • 70aarcuda

        70aarcuda Master Hoader of SBM FABO Gold Member

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        I provide this for some people wanting to know if using scat i beam rods and light piston you could internally balance a cast 360 crank without mallory....But you got get your big fucking ego in the way of everything...You talk shit all the time...but never post of picture of any shit you got....so Fuck OFF....
         
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        • 70aarcuda

          70aarcuda Master Hoader of SBM FABO Gold Member

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          the ignore button is a wonderful tool.........
           
        • nm9stheham

          nm9stheham Well-Known Member

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          If money was all we cared about, we wouldn't be doing any of this.
           
        • 19DUSTER73

          19DUSTER73 Well-Known Member

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          We are talking factory cast cranks correct?
           
        • yellow rose

          yellow rose Doctor of Thinkology.

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          Right back at hero boy. Keep running on stupid. It works for you.
           
        • 70aarcuda

          70aarcuda Master Hoader of SBM FABO Gold Member

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          yes...stock oem crank...
           
        • dadodgekid

          dadodgekid When in doubt... floor it

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          False... he posted a pic of his car in another post....
           
        • Cudafever

          Cudafever Well-Known Member

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          I for one, was one of the people that wondered if today's much lighter piston and rod would have been enough, guess not.
          Maybe with alu rods.......:thumbsup:
           
        • 19DUSTER73

          19DUSTER73 Well-Known Member

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          I had my scat 9000, scat I beams and kb191s balance out with no weight added. BUT the 9000 is internal balanced by design. never had it next to a stock one to see the differences. When weighed it came in at around 54 lbs while the stocker was 59ish. Good thread. Caused me to do a little research about balancing. I don't know much about balancing but know a little more now lol.
           
        • dusterdoug

          dusterdoug Well-Known Member

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          So back to my question: what is SAFE operation for an external balanced 360 with OE crank? Weighted balancer/sculpted flex plate.
           
        • 70aarcuda

          70aarcuda Master Hoader of SBM FABO Gold Member

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          dont know...never broke a 360 oem crank whether it was internally or externally balanced...sometimes I fell stupid and what to spend money uselessly and internally balance the crank...

          my 71 demon and 71 duster are externally balanced...71 dart in internally balanced....also have an internally balanced crank in another engine...this crank is going in a short block to replaced the short block in the 71 dart...hence...already have balancer and flex plate for internally balanced crank.

          Back in the 90s was spinning a oem 360 internally balanced crank 7500 rpm...stock rod broke...crank survived...and it had heavy trw domed pistons..