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    Honing/Boring block and other questions

    Quick question regarding the block.

    I was going to have my block honed, so I could still reuse my SuperEta pistons.

    HOWEVER, my friend brought up a good point. As soon as you resurface (hone/bore) the cylinder walls, the pistons will no longer be compatiable, due to tolerance issues. Is this true?

    Basically, if I wanted to resurface my cylinder walls (say the crosshatching was non-existant) I would need new pistons to put in - rendering my SuperEta pistons useless. if i want to use my SuperEta pistons, I have to leave the block as is.

    Additionally - I'm planning on reusing my rods. If I stick with the SuperEta pistons (thus not honing or resurfacing my cylinder walls) I don't need to remove the piston from the rods right? This would mean I wouldn't need new pins or bushings correct? Or should I just replace those anyway?

    I've been doing lots of research lately, and little questions have popped up here and there.

    Thanks!
    - Sean Hayes

    #2
    I don't think so, if they are just honing I think you can (well you have to) get plus sized rings. I bet if you called a machinist they'd be able to tell you for certain. ;)

    how many miles are on your engine? there's probably nothing wrong with them, but why take apart the whole motor and then use old, replaceable parts? It probably doesn't cost too much either.
    Build thread

    Bimmerlabs

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      #3
      You mean why reuse the pistons?

      Well...if I can reuse the pistons, I'm all for that - and replacing everything else. i was looking for suggestions.

      So - I CAN reuse the pistons, if I have the block honed out, I just need new rings?

      See..that made sense to me.

      I'm going to dismantle the block, bring the bototm end in and lots of other parts to have them clean and check out.

      So, what I can probably do is have the block honed, get plus sized rings, and reuse the pistons, correct?
      - Sean Hayes

      Comment


        #4
        call a machinist, they will have to do the honing anyway, and they will be able to tell what you can and cannot (or should not) reuse. and do not reuse your rod bolts! :)
        Build thread

        Bimmerlabs

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          #5
          Originally posted by nando
          call a machinist, they will have to do the honing anyway, and they will be able to tell what you can and cannot (or should not) reuse. and do not reuse your rod bolts! :)
          Didn't plan on it. i was only planning on reusing the rods, that's it.

          I will do just that.

          Thanks nando!
          - Sean Hayes

          Comment


            #6
            Show me a parts place that sell plus-size rings for an M20.


            If the cylinder bores are in good shape, with no ring groove at the upper end of the bore, and bore taper is within spec, then you are fine with a light honing of the bores, and new rings (I've never seen plus-size rings for a BMW engine- maybe a fat model gets one from her fiance??).

            So, like Nando says, find a good machinist to take the parts to, he/she should be able + willing to advise you what you can/cannot and should/should not do based on the condition of the parts you give him.

            FWIW, take your pistons with you too, and ask the machine shop to check them out to make sure they are OK to reuse.

            Bret.

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              #7
              Yep...I'm taking EVERYTHING there. I just got to get it apart first. He said they could check out everything and clean it for it. So, that's the plan.
              - Sean Hayes

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                #8
                Forgot about this.

                I had an idea. I have the 325is block from my parts car.

                Could I strip that block down and bring it in and have them bore that out to fit my SuperEta pistons (if they are confirmed to be good) with normal rings? Would that be better than having them hone it - or will it be about the same anyway?
                - Sean Hayes

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                  #9
                  Originally posted by Sean
                  Forgot about this.

                  I had an idea. I have the 325is block from my parts car.

                  Could I strip that block down and bring it in and have them bore that out to fit my SuperEta pistons (if they are confirmed to be good) with normal rings? Would that be better than having them hone it - or will it be about the same anyway?

                  The bore diameter is the same- so I would use the block that the pistons came from, if possible.


                  Bret.

                  Comment


                    #10
                    Originally posted by Rigmaster
                    The bore diameter is the same- so I would use the block that the pistons came from, if possible.


                    Bret.
                    Oh, are they? So, it's just different pistons then?

                    Well, that would be pointless - lol

                    Sounds like a plan, I'll just have it honed then. Honing allows me to use standard rings, correct? Since it doesn't remove enough material to warrant oversize rings.
                    - Sean Hayes

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