1. yellow rose

    yellow rose Overnight Sensation FABO Gold Member

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    Anyone want to guess what these numbers are, and what they respectively represent? No poll this time. Cake won the last one hands down.

    4143A96F-3B04-4DC9-AC51-51723653D692.jpeg
     
  2. RammerJammer75

    RammerJammer75 Well-Known Member

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    You're doing Common Core math?

    But in all seriousness the only one I have a guess on is RA for the surface finish on the deck.
     
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    • lilfontleroy

      lilfontleroy annoyinglilLeroy FABO Gold Member

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      I see why you have trouble finding your "notes"... :poke::poke:

      rear end bearing and pinion gear runout #'s?
       
    • CFD244

      CFD244 FABO Gold Member FABO Gold Member

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      Muffler bracket for a '78 Pinto?
       
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      • Cuda416

        Cuda416 FABO Gold Member FABO Gold Member

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        Ok, I will admit first off, I cheated. Still learned something new though. Not gonna spoil it though.
         
      • Dicer

        Dicer Diceman FABO Gold Member

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        RPK should read 7.62
         
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        • yellow rose

          yellow rose Overnight Sensation FABO Gold Member

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          You are VERY close. Think “hole” rather than flat.
           
        • RammerJammer75

          RammerJammer75 Well-Known Member

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          Finish for the cylinders?
           
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          • Treblig

            Treblig Well-Known Member

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            • Dana67Dart

              Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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              Surface texture parameters
               
            • Cuda416

              Cuda416 FABO Gold Member FABO Gold Member

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              Surface texture measurements (peaks/valleys and means) of a honed cylinder.
               
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              • yellow rose

                yellow rose Overnight Sensation FABO Gold Member

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                That’s what those numbers are. The four most important numbers for cylinder finish.
                 
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                • dano

                  dano Evil Handy Man

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                  Like Cuda416 said, those are surface finish roughness tolerances if you were to measure the surface with a profilometer.

                  I'm helping my son do common core math right know and I feel like jumping out the window. Its like they ask a Doctorate level psychologist to rewrite math. It is a giant load of BS.
                   
                  Last edited: Nov 23, 2020
                • Dana67Dart

                  Dana67Dart Like a fine wine, only getting better with age! FABO Gold Member

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                  A lot of common core math is just mental math but on paper.

                  I was never good at mental math but the more I use it the easier it is to do
                   
                • '63GT

                  '63GT FABO Gold Member FABO Gold Member

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                  Did you get a new toy YR ? :lol:
                   
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                  • MOPARMAGA

                    MOPARMAGA FABO Gold Member FABO Gold Member

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                    What do the letters & numbers stand for ?
                     
                  • yellow rose

                    yellow rose Overnight Sensation FABO Gold Member

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                    I wish. My old boss bought a new hone and the profilometer so I had him touch up the bores on my junker for me and he gave me the numbers. Way too much fun (and work) to keep up with current technology.
                     
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                    • yellow rose

                      yellow rose Overnight Sensation FABO Gold Member

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                      Ok, off my memory so remember that...

                      Rk is the core roughness value. It gives you the idea of how rough (or fine) the finish is, but without the other numbers it doesn’t mean too much. I mean it’s important but you can’t really define what you have without the rest of the numbers.

                      Rpk is the distance from the mean on the Y axis to the highest peak.

                      Rvk is the distance from the mean on the Y axis to the deepest valley.

                      Ra is the arithmetic sum of the absolute values of the peaks and valleys over the length of the measurement.

                      Keep in mind the mean for RPk isn’t the same mean as Rvk, because the mean line is related to the average of the distance across the peaks and the Rpk mean is the average of the distance of the valleys.

                      Now, to evaluate all that math requires knowing what rings you have, piston speed, the hardness of the block, fuel used, NA or power adder...and probably some other things I’m forgetting.

                      The best thing to do is call your ring manufacturer and tell them what you are doing and they will tell you what the finish SHOULD be.

                      Hitting those numbers can be a bear if you haven’t honed that particular brand of block or sleeve before or if the manufacturer changes the hardness of the block or sleeve. Compacted Graphite blocks do not hone the same as the run of the mill SBC block, which happen to be the softest blocks (BY FAR) of the big 3, with Chrysler being the hardest and Ford not far behind.

                      Any aftermarket race block should be harder than an OE block. That changes the finish required.

                      And I can say after watching the new hone work that it’s near impossible to get the numbers correct on a non CNC machine and especially with vitrified abrasives.

                      The profilometer doesn’t lie. I also forgot even the engine oil used can change the surface finish.
                       
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                      • MOPARMAGA

                        MOPARMAGA FABO Gold Member FABO Gold Member

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                        Wow Tim, that's quite some brain you have !
                        Thank you for the reply, way over my pay grade as a carpenter/mechanic lol. But I appreciate it nonetheless
                         
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                        • Treblig

                          Treblig Well-Known Member

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                          Here's a pic of what the profilometer sees (measures). The peaks and valleys and well as overall flatness/waviness (or deviations there of).

                          FYI - These pics are a surface that is greatly magnified:


                          images?q=tbn:ANd9GcTFNIcu3TmVkIOWJuSyKOClbcXuZ_buucBoiA&usqp=CAU.jpg

                          images?q=tbn:ANd9GcRcO0cDA51GzYW_cFCFl3xPUFwVqROs0mnfKg&usqp=CAU.jpg





                          images?q=tbn:ANd9GcSaow5nnT2YifBSGMyDZjWCubIxPkKmjPUE3g&usqp=CAU.png
                           
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                          • MOPARMAGA

                            MOPARMAGA FABO Gold Member FABO Gold Member

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                          • Treblig

                            Treblig Well-Known Member

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                            You look at and see and feel a surface, like a freshly bored and honed cylinder, and it looks smooth and flat and shiny.................................but it's actually extremely rough and not very flat. The machine shop does its' best to get it as uniform and smooth as possible but the profilometer does not lie!!!
                            Remember - if it was too smooth the rings would never seat!
                             
                          • MOPARMAGA

                            MOPARMAGA FABO Gold Member FABO Gold Member

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                            Okay yeah that makes sense, machining is a trade I'd love to get into..so how does the profilometer work ? Is it like a radar reading depths?
                             
                          • Treblig

                            Treblig Well-Known Member

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                            using a profilometer - Google Search
                             
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                            • pishta

                              pishta I know I'm right....

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                              Dingle ball hone and iron rings...... Lather rinse repeat.....good for another 50K. What emissions? Farmer John.
                               
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                              • MOPARMAGA

                                MOPARMAGA FABO Gold Member FABO Gold Member

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