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Thread: Forged Piston ring wall clearance

  1. #1
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    Forged Piston ring wall clearance

    what piston to wall clearance, are people* running? I've got cp pisston, cp recommend .0045 piston to wall clearance.

    my friend's build ej25 has cp piston and has 3.5 thou piston to wall clearance, on cold start piston slapping against bore very loud, he also has oil consumption issue's.

    Would having 2.5 thou piston to wall clearance to tight?

  2. #2
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    What material is the piston made from, 4032 or 2618 ?

  3. #3
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    Quote Originally Posted by Motors S GT View Post
    What material is the piston made from, 4032 or 2618 ?
    2618

  4. #4
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    Quote Originally Posted by jl-wrx View Post
    2618
    If its a none competition, road use on pump fuel, with sensible boost & std compression ratio, 0.0025" will be fine, Mahle 2618 you can run on a 2.5 engine as low as 0.002" as a std build spec, check the gudgeon pin wall thickness on CP pistons as in my experience they are couple mm thinner than most other pistons, & have failed.

  5. #5
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    Quote Originally Posted by Motors S GT View Post
    If its a none competition, road use on pump fuel, with sensible boost & std compression ratio, 0.0025" will be fine, Mahle 2618 you can run on a 2.5 engine as low as 0.002" as a std build spec, check the gudgeon pin wall thickness on CP pistons as in my experience they are couple mm thinner than most other pistons, & have failed.
    Car be use for week and the rare occasional drag and track. Running on flex pump fuel and pump e85, boost 28psi max and compression ratio it be close to sti stock. Do you know by memory the gudgeon pin wall thickness of the other piston ?so i can check it with the cp piston i got.

  6. #6
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    I would use 0.003" as a minimum clearance for 28psi, pin wall thickness is 5.2mm to 5.5mm on Wiseco, Mahle, & OE gudgeon pins, the last CP ones supplied to me were 4.3mm.

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