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

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    #76
    I get what you're saying. Smooth transitions are always best. On mine, with the 89.6 mm crank and s52 rods, it was only the raised text on the shaft that was making contact every couple revolutions. It was barely anything. All that was really needed was to knock down the text on a lathe. For an even bigger crank do like you said and remove the required material in a localized area then blend it all out to have nice smooth transitions.

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      #77
      Stickied.

      SILBER COMBAT UNIT DELTA (M-Technic Marshal)
      RTFM:http://www.r3vlimited.com/board/showthread.php?t=56950

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        #78
        dumb question what is the thing between the bearings. it looks like it has been added and looks like a cam lobe of sorts

        http://www.ecstuning.com/BMW-E30-325...w_All/ES23062/
        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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          #79
          Wow that's odd. Definitely looks like a hard weld cam lobe. For what though. That's no good for bigger cranks.

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            #80
            Originally posted by digger View Post
            dumb question what is the thing between the bearings. it looks like it has been added and looks like a cam lobe of sorts

            http://www.ecstuning.com/BMW-E30-325...w_All/ES23062/


            Bizarre.

            It looks like a fuel pump lobe maybe but M20 never had a mech one....
            Lorin


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

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              #81
              unless its something machined to give a smooth surface for a weld. Looks like lots of penetration on either side of the "lobe", a lot of heat has been transferred here.

              Edit: Looking at the other pics, it's certainly eccentric in shape. Very weird.
              Just a little project im working on
              - http://www.lse30.com -

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                #82
                Getting closer to building mine out and wanted to know for sure so picked up a pair of 300mm calipers and gave it check, this is an 87 b25i block not cleaned.

                My M20 Frankenbuild(s)
                4 Sale - Fully Built TurnKey Megasquirt Plug and Play EMS

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                  #83
                  Originally posted by digger View Post
                  hiop used to do a 91mm and 95.8mm for the M50/M52 stokers
                  BMW made a 93.8mm stroke for the S52 block that went into an ALpina B3 3.3 and B3S
                  MM do an offset ground S54 crank (s54 has bigger rod bearing so can be offset down the M50 size while increasing the stroke) for M50 based engines with 93mm stroke but adapting the nose is an issue
                  also VAC are taking preorders for a 97mm crank for M50 based engines but this wont fit i would say. you also be looking at $5500 to get your hands on one yikes....
                  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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                    #84
                    Originally posted by tinkerputzer View Post
                    Definitely looks like a hard weld cam lobe.
                    Ehh, no... This is a heat treating process called induction hardening...



                    sigpic

                    A man chooses, a slave obeys... Would you kindly?

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                      #85
                      nevertheless if you buy one from the dealer you get the same thing and the shaft in that area is smaller at D18mm either side of the lobe in the new ones
                      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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                        #86
                        I have an 89.6mm crank in my 325iX. Used some H Beam rods and it was interfering with the bottom of the cylinder bore. But, I did not have clearance issues with the Aux Shaft, which is slightly different in the iX over the i models. I believe it rotates the other direction from the stock 325i's.

                        Nando's post and picture of this:

                        http://www.r3vlimited.com/board/show...1&postcount=42

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                          #87
                          Ted, did you clearance the bottom of the block or the rods?
                          ...what hasnít been done to an m20 yet?

                          m20 Oil Stencil

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                            #88
                            Originally posted by LEANE30 View Post
                            Ted, did you clearance the bottom of the block or the rods?
                            Clearanced the bottom of the block. I believe the larger bore wouldn't have caused a problem but I bored after clearancing for the rods. It was very minimal, like one piston cleared on the whole rotation, but the second one didn't.

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