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Stroking/boring M20B25/B27: Sectioned blocks show critical dimensions. PICS!

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    #16
    you shouldn't have to cut into that part of the block if you use the 89.6mm crank and S52 rods. AFAIK you only need to clearance things with the 84mm crank because the counterweights are larger in diameter.
    Build thread

    Bimmerlabs

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      #17
      When i test fit my engine (89.6mm crank and s52 rods) using the stock pistons the rod shoulder was just kissing the bottom of the bore. This was while it was still stock 84 mm bore. So i figured once it was bored to 86mm it would be fine. I cleaned up some of the rough casting lines at the bottom of the bore just to be safe though. Clearance at final assembly was some where around .020"-.030"

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        #18
        Originally posted by nando View Post
        you shouldn't have to cut into that part of the block if you use the 89.6mm crank and S52 rods. AFAIK you only need to clearance things with the 84mm crank because the counterweights are larger in diameter.
        some aftermarket rods have larger shoulders than the OEM rods especially H-Beam rods with unnecessarily wide beams , among other reasons ;)
        89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

        new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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          #19
          i have a junk eta block with the big plug at the back. im gonna cut this bitch up. suggestions and what do people want to look at?

          ill measure

          -deck height
          -cylinder height
          -bore wall thickness between and on thrust and no thrust side
          -position of oil gallery relative to bore
          -position of oil gallery relative to bottom of crankcase
          Last edited by digger; 01-25-2014, 12:30 AM.
          89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

          new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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            #20
            I'm interested in the oil gallery to bottom of bore dimension. That is where the supposed internal clearance benifits of the eta block are.

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              #21
              Originally posted by tinkerputzer View Post
              I'm interested in the oil gallery to bottom of bore dimension. That is where the supposed internal clearance benifits of the eta block are.
              is my biggest question to will do.
              89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

              new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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                #22
                B27 Exhaust Side External View


                B25 Exhaust Side External View


                B27 Intake Side External View


                B25 Intake Side External View
                89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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                  #23
                  B27 oil gallery plug i pressume also big welsh plug on eta


                  B25 oil gallery plug i pressume


                  nothing drastically different.
                  89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                  new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                  Comment


                    #24
                    The deck height on these blocks are as follows

                    B25 206.2mm
                    B27 206.0mm

                    cant comment of whether material has been removed

                    the depth of the bore on both is the same at 134.5mm
                    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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                      #25
                      A 90* piece cut from the B27 block. cyl 1 exhaust side. 5.5mm is the thinnest area half way up.



                      view showing wall thickness at front of bore near where water pump sits. this are is thinnest 4.8mm half way up. is probably the least important areas except for turbo guys



                      the intake side quarter cut off sits ontop of the block. alot of meat here 6.3mm



                      a completed cut through cylinder 1



                      so the oil gallery is much the same position.
                      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                      Comment


                        #26
                        Nice work digger.
                        Lorin


                        Originally posted by slammin.e28
                        The M30 is God's engine.

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                          #27
                          Way to go mate. This puts some things to rest.

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                            #28
                            So the b25 would be better suited for boost?

                            Sent from my Nexus 5 using Tapatalk
                            My Feedback Thread

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                              #29
                              there are some internal difference which might have a minor effect on fitting the big counterweight 84mm stroke crank. nothing some grinding wouldn't fix
                              89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                              new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                              Comment


                                #30
                                Originally posted by spoolinspoon View Post
                                So the b25 would be better suited for boost?

                                Sent from my Nexus 5 using Tapatalk
                                i would think its much of a muchness.
                                89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                                new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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