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b18c stock size or 81.5mm pistons?

Discussion in 'Forced Induction' started by bvtec, May 24, 2005.

  1. bvtec

    bvtec Senior Member

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    Hi, i have decided not to sleeve my b18c and i am just about to get the pistons for it. I was thinking about keeping the stock piston size and not boring the sleeves any further but friends are advising that i bore to at least 81.5mm,will that not weaken the sleeves further?.
    can anybody see anything wrong with sticking to the standard bore when installing the pistons etc(81mm)? :blink: <_<
     
  2. pissedoffsol

    pissedoffsol RETIRED

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    thinner = weaker.

    there is no good reason to go to 81.5
     
  3. bvtec

    bvtec Senior Member

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  4. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Take your block to a good machine shop and see if you need to bore it out any to clean up any damage in the cylinder walls. If not, stay at the stock bore. With forged pistons, you'll have to go slightly larger anyway because of piston expansion, so you'll still bore some- just not enough for anyone to say that you went from 81 to 81.5.
     
  5. bvtec

    bvtec Senior Member

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    ok so just say that i dont bore out the stock sleeves. And i just make sure that i hone, if i leave the sleeves at stock bore which i think is 81mm what piston size will i require??
     
  6. K2e2vin

    K2e2vin Senior Member

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  7. bvtec

    bvtec Senior Member

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    huh so im a little confused i thought id have to go slightly bigger^^? :unsure:
     
  8. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    Forged aluminum alloy pistons expand more when they get to operating temp than cast aluminum pistons- so they'll need more piston to wall clearance. A forged piston that's 81mm cold will be larger at operating temp than a cast 81mm piston, so your cylinder walls must be bored to match.
     
  9. bvtec

    bvtec Senior Member

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    so what size pistons do u advise me to get for my stock b18c??
     
  10. wannaberacer

    wannaberacer Member

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    go to the machine shop, have them hone it, maybe bore it if they need to. They most likely will bore it .020 over. Hence, go to wiseco and order some .020 pistons. If they said the bore is still 81mm(and didn't bore it_, then get the stock bore ones....just ask the machine shop after they're done....
    P.S. the guy I know at napa charges me 20 bucks a cylinder, plus 25 for hot tanking. He may just be hooking me up since I know him, but its not expensive to have a machine shop do that for you.
     
  11. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    No- check the bore with a micrometer, then order your pistons to match. If your stock sleeve is still in good shape, you can probably get away with 81mm. I would just run 81.5mm and be done with it. Once you get your pistons, take the pistons to the machine shop with the block and have them match bore the block to the pistons. Do NOT bore before you get your pistons- you'll just have to take it all back to the machine shop if you want it done RIGHT.
     
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