1. 4spdragtop

    4spdragtop Well-Known Member

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    Maybe...but if they are lightening it, they are removing metal correct?
    I've never heard or seen a balance quote on a piece of paper. So I cant say one way or another. I can only imagine that there is a fair amount of calculations and weighing involved, which equals a lot of time=$$
     
  2. RustyRatRod

    RustyRatRod Weenie idiot loser. FABO Gold Member

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    Well it depends, Steve. They may need to remove metal from one side and add to the other. It's all about gettin the bob weight right. Sometimes it's a trick.
     
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    • nm9stheham

      nm9stheham Well-Known Member

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      FWIW...... 50% of the piston weight change is doubled because there are 2 piston/rod assemblies represented by each bobweight. So, if you're thinking of it in that fashion, then think of 100% of the piston weight change going into the bobweight.

      The over- or under-balance creates a rocking motion in the engine at the same rate as the RPM's. Imagine passing an imaginary axle through the #3 main bearing, and the engine rocking back and forth on that... .front is going up while rear is going down and vice versa, back and forth once per crank rotation. The trannie and its mounts tends to limit this rocking motion, but then those forces all go into the front and rear of the bearings, crank, block etc.

      The balancing of the piston/rod assemblies minimizes a different imbalance around the main axis of the crank.
       
    • Wyrmrider

      Wyrmrider Well-Known Member

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      good on you NM
      one poster said no big deal
      going lighter maybe so
       
    • yellow rose

      yellow rose Doctor of Thinkology.

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      I've already posted...the math is simple. Takes no time.
       
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      • 4spdragtop

        4spdragtop Well-Known Member

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        Math might be simple, but the time it takes to come up with numbers to plug in??
        Gotta weigh every single piece right?
         
      • yellow rose

        yellow rose Doctor of Thinkology.

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        Yes. But I seperate out the math from the time to weight and equal each part. Today we are pretty lucky. Most Pistons and rods are now well within a gram. So you are really just making sure something from a different run didn't get boxed together.

        Once you have the big end, pin end, piston, rings, pin, pin retaining clips and a rod bearing weighed, you take about 5 minutes to add up the bobweight.

        Then the real work begins.
         
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        • 89on35s

          89on35s Inferno Red Duster FABO Gold Member

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          I can't remember who, but someone I was talking to out at the track recommended Precise Engines to me for my Car engine stuff. I have used them in the past, but it was for Snowmobile stuff. @79410aspenrt do you have a recommendation?

          Cley
           
        • Mopar Sam

          Mopar Sam Well Fed Member

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          I really wish the crank manufacturers would make cranks unbalanced for machine shops, especially the cast versions. I hate when you need to add weight right where they drilled a hole. Usually this is on stuff with hyper pistons and cast cranks.
           
        • nm9stheham

          nm9stheham Well-Known Member

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          FWIW...... Getting the end weights for stock rods matched can be time consuming.
          They will vary a fair amount. Checking 1 set of light SBM rods yielded bobweight variation of over 20 grams across the set if the piston and pin weights were all identical. So yes IMHO, lots of labor there.

          And for info.... The rod end weighing part is the area most subject to errors.
           
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          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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            I agree, but what RRR is saying is that IF you need to add metal...... I don’t think anybody will give a quote on the dollar amount and much less stock to it. Typically, I get, it starts at $ XXX ....

             
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            • 79410aspenrt

              79410aspenrt Well-Known Member

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              i have used Precise Engines in the past. i don't think i will go back there. i recommend Bruce from ABS in regina. but he's a one man show and it takes time, lots of time. i have used Northside Engines for some small stuff.
               
            • 89on35s

              89on35s Inferno Red Duster FABO Gold Member

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              Was it a particular issue with Precise? I know they are expensive but I have been happy other than that.

              Cley
               
            • oldkimmer

              oldkimmer FABO Gold Member FABO Gold Member

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              I guess it all depends if u want to ship or travel. Yes, Bruce is the best. I hear Northside does good work but I haven’t used them. Kim
               
            • 70aarcuda

              70aarcuda Master Hoader of SBM FABO Gold Member

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              this is what i get from the machine shop along with the bill....print out of the balance job...plus he keeps one on file for the future should something needs to be fixed. This a 360 .070 small block cast crank that had been previouly internally balanced. New pistons weight pretty close to old pistons but went from a 660 gram H beam rod to a 595 gram I beam rod. Weight had to be removed from the crank....I wonder if i could have gotten a rebate on the mallory metal...lol

              20171031_210729_resized.jpg
               
            • 70aarcuda

              70aarcuda Master Hoader of SBM FABO Gold Member

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              I can not find the second sheet where they spin it and shows the numbers.....
               
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              • 89on35s

                89on35s Inferno Red Duster FABO Gold Member

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                Well I got it tore down completely now. I'm going to follow along with @krazykuda and his awesome how to that he was kind enough to put together. So far the crank bearing surfaces look awesome. Both the crank and bearings are marked .010 so I know what main bearings to get now. The rod bearings are not marked but I can read the part number. I have yet to try and find what they are.
                20191201_151035.jpg 20191201_151043.jpg
                The bores look good at .030 over. I'll hone them up and drop new pistons in with the stock rods and ARP rod bolts. I ordered most of the stuff I need like pistons, rod bolts, oil pump, etcon Summit's black friday sale saving a whopping 50 bucks but free shipping to Canada is always sweet!
                20191201_155400.jpg
                If anyone wants a used MP 508 cam it's out and available too.
                20191201_160614.jpg
                Looks like a new double roller in it so that is a bit of a bonus too! All in all it was a good couple hours in the shop!

                Cley
                 
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                • rumblefish360

                  rumblefish360 So close, yet so far away FABO Gold Member

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                  Good bracket cam.
                   
                • krazykuda

                  krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                  If there are no size markings on the bearings, they are usually standard, however I would recommend measuring the journals to be sure....
                   
                  Last edited: Dec 1, 2019
                • oldkimmer

                  oldkimmer FABO Gold Member FABO Gold Member

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                  Cley, u can buy new rods on Speedmaster 79. For less than $200.00
                   
                • 89on35s

                  89on35s Inferno Red Duster FABO Gold Member

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                  I've got 2 sets of stock rods and the ones in my car as well. Is there a benefit to new rods?

                  Cley
                   
                • oldkimmer

                  oldkimmer FABO Gold Member FABO Gold Member

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                  No cycles on them and ur stock ones will be as much once u resize them and new bolts
                   
                • 89on35s

                  89on35s Inferno Red Duster FABO Gold Member

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                  Good to know! If you're in town some time you should stop by for a Christmas drink and give me a second opinion on what I have!

                  Cley
                   
                • oldkimmer

                  oldkimmer FABO Gold Member FABO Gold Member

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                  Cley, U got it buddy. Kim
                   
                • krazykuda

                  krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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                  However, I prefer to use rods with oil squirt holes and many of the aftermarket rods do not have them... That's why I prefer to recondition old rods and have new bolts installed so I can have squirt holes....


                  but if you don't want oil squirt holes then look into new rods...
                   
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