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Cylinder bore 1800

posted by  jaydee on  Tue Nov 23 17:41 CST 2004
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last visit: Thu Oct 23 23:45 CST 2014
[RELATED]

I did a quicky check (in the dark, in the cold, with a so-so caliper) on the bore of the engine I have on a stand in my shop. The readings were 89.58, 89.56, 89.57, and 89.57. I don't have my books in front of me, but as I recall the standard bore for the B20 is around 88.9? Is that correct? What sort of overbore do I have here? It seems fairly miniscule to me.
Thank
JD








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    Cylinder bore 1800

    posted by  Bennie on  Tue Nov 23 23:41 CST 2004
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    last visit: Wed Nov 28 03:03 CST 2007
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    The B20E has 88.92mm bore. B20A and B have 88.91mm. Maybe yours has 0,5mm oversize? If it does, the piston markings will you so.
    Might aswell be just worn cilinders, allthough the readings are remarkably close... (0,5mm is indeed a very small oversize, normally 1mm is the first oversize on these engines)

    Cheers, ben

    --
    P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)








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    Cylinder bore 1800

    posted by  chakra on  Tue Nov 23 18:16 CST 2004
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    The pistons should be stamped if they are oversized, I believe. Would be more accurate to look for that marking than to trust a not-so-good caliper gauge in the dark.








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      Cylinder bore 1800

      posted by  someone claiming to be JayDee24Ca on  Wed Nov 24 03:34 CST 2004 [RELATED]

      Thanks Chakra;
      I went back in this morning with a trouble light and the piston tops are marked +0.30.
      JD








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        Cylinder bore 1800

        posted by  Bennie on  Thu Nov 25 06:54 CST 2004
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        +0.30 or +0.03 ?

        -If it's +0.03" it sounds pretty odd to me. Since 88,9 is de standard bore and yours is 89.58, 89.56, 89.57, and 89.57, your bore is about 0,67mm larger then stock. But +0.03 is 0,76mm which means the tollerance you currently have is less then it should be... (or maybe you measured the carbon build up at the top of the bore?)

        -If it's +0.30mm is also sound odd, since I have never seen 0,30mm oversized pistons.

        Hmmmm, cheers, ben

        --
        P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)








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          Cylinder bore 1800

          posted by  mjamgb on  Tue Nov 30 11:15 CST 2004
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          last visit: Tue Sep 4 14:53 CST 2012
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          LOL +30 in the USA means 0.030 INCH overbore and is very common (and also what I suspected when doing the math from his measurements).

          Mike!
          --
          Mike!








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            Cylinder bore 1800

            posted by  Bennie on  Fri Dec 3 03:38 CST 2004
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            Yeah, ok.
            My point is: 0.030 inch overzised pistons. But the cilinder bore has ben measured less then 0.030 inch overzise, which would imply quite a bit less then stock tollerance! (0.10mm less)

            cheers, ben
            --
            P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)








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              Cylinder bore 1800

              posted by  mjamgb on  Fri Dec 3 12:50 CST 2004
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              last visit: Tue Sep 4 14:53 CST 2012
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              A shop worth it's salt will request the replacement pistons before honing to size so they can set the clearances to each piston precisely. "30-over" is a target and a nominal size. The application dictates the actual dimension of the piston and a similar oversize for a nominally similar bore may be several thousandths different.

              So, it was likely just fine.

              skirt clearances of 0.005" (0.13mm) are common and actually fairly "loose."

              Mike!
              --
              Mike!







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