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  1. #1

    Big Bore Pistons Over 88mm

    I'm making a custom made big bore engine and would like to know who makes pistons sizes over 88mm?

    So far I've found the Group-K big bore pistons in the 88.5 & 89mm sizes and the flat top piston from Japan made for the Fennec Group in the 88mm & 89mm sizes.

    I'm just wondering if I have any other options out there and help would be appreciated.


  2. #2
    westy's Avatar
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    conntact HopatcongGPR from this forum he had 90mm pistons made for the GPR

  3. #3
    vomitspot's Avatar
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    what motor platform are you working with ?
    fentec is prob 62t based
    the 87and up from everyone on here is gonna be gpr platform

  4. #4
    Quote Originally Posted by westy View Post
    conntact HopatcongGPR from this forum he had 90mm pistons made for the GPR

    I'm very curious about those custom made pistons and that might be a good option.

    Quote Originally Posted by vomitspot View Post
    what motor platform are you working with ?

    It's going to be used in a 65U, 62T, 61X cylinders with custom made sleeves and possibly with a stroker crank setups.

    Quote Originally Posted by vomitspot View Post
    fentec is prob 62t based
    the 87and up from everyone on here is gonna be gpr platform
    The Fennec flat top pistons are very similar to the Riva or R&D flat tops and available from sizes 84mm to 89mm.

    I just don't like having to spend 270 bucks per piston plus shipping for Japan and I'm searching for a cheaper option.

    I've also hear some engine builders use the CR500 and 951 pistons in these engines.

    What's the largest GPR piston available?

  5. #5
    Here come the smokers! OBXJeepGuy's Avatar
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    Quote Originally Posted by vomitspot View Post
    what motor platform are you working with ?
    fentec is prob 62t based
    the 87and up from everyone on here is gonna be gpr platform
    Group K does the 89.5, and 90mm for the 62T and 64X cylinders.. The way I am going.

  6. #6
    sleeplessnMS's Avatar
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    I think the 87mm is the going thing..... Easy availability and $150. Its all in porting aswell but most great #'s are done with stock stroke an 87's....

  7. #7
    vomitspot's Avatar
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    just consider the piston pin size /bearing are different in the 65u and the 66v
    be sure your buying what you need not just a big piston

  8. #8

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    it may be small by you big builders standards, but what is out there for a 83-84.5MM piston..forged...and maybe a little more compression then the stock gpr1200 piston? something cheaper(cheap and forged..ya right..LOL)...i would settle for a good hyperutectic piston for cheap if i can find something. you guys are the experts..what is out there..thanks alot and ttyl
    john

  9. #9
    Flying Scotsman's Avatar
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    I am running 85.5mm pistons in the 97 GP for now I will be going 86mm in the future.

    On a 1200

    Stock GP 1200 piston 84mm 1131cc
    .060 over piston 85.5mm 1169cc (bore size now)
    .080 over piston 86mm 1184cc

  10. #10
    Me Hahn and Joe H204YOU's Avatar
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    Quote Originally Posted by deereman View Post
    it may be small by you big builders standards, but what is out there for a 83-84.5MM piston..forged...and maybe a little more compression then the stock gpr1200 piston? something cheaper(cheap and forged..ya right..LOL)...i would settle for a good hyperutectic piston for cheap if i can find something. you guys are the experts..what is out there..thanks alot and ttyl
    john
    Hyperutectic pistons tend to be brittle due to there higher silicon content and fail quick if theres any pre-ignition.Might be ok in a stock motor tuned rich,but in an overbored hot rod,Id think they would be trouble.Thats my 2 cents.Hopatcong(Dan) has done his homework with wiesco on the 90mm,and the 87mm group k's are the standard BB choice.Hope this helps.

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