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Thread: Piston to cylinder wall clearances for forged pistons

  1. #1
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    Piston to cylinder wall clearances for forged pistons

    Hello. I have just received Wiseco forged pistons for my engine and I would like to get to know what clearances between pistons and cylinder walls I should do. Wiseco suggests 0.0030” on the paper I got. I’m going to boost max 1.0bar and drive the car daily after rebuilding the engine. Sometimes a few races on a track. What clearances did you do in your BMWs? I know that Wiseco gave me a suggested clearance, but for example JE or CP gives you a few suggested clearances for different setups. Wiseco gave only one, that is why, I would like to read about yours. Thanks in advance for your help.

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    I followed the Wiseco suggestions/paper on mine and they are working great so far. Just a bit piston slap at mornings but nothing like a diesel engine noise for sure.
    Euro M3'87 NogaroSilver/Euro E34 M5 '93/Porsche 993 TT 97' Euro/Porsche 993 Carrera 95' Euro/Skyline R33 GT-R


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    I took my 87mm Wisecos and block to a reputable machine shop (scca, imports, good ole boys you name it) and the machinist asked me for the clearance spec paper. I handed to him and went from there. I installed my rings according to the FI spec numbers for gap and I just did a compression spec a few days ago after about 1000 miles and everything was rock solid.

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    Just be careful with this as I have a Honda friend that has had his pistons expand quite a bit leading to block and piston damage.

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    We set the CP pistons to 0.0035” as the spec sheet recommends.
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  6. #6
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    Ok. Thanks guy for answers. What about piston rings clearances? Didnt get any information about them from the Wiseco.
    I also have question to you with regard to the Wiseco piston. Stock BMW pistons have arrows and those arrows must be pointing towards camshaft drive while installing. I can’t find any marks on the Wiseco piston. Is there a difference which side of the Wiseco piston will point towards camshaft sprockets?

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    Quote Originally Posted by Maleckis View Post
    Ok. Thanks guy for answers. What about piston rings clearances? Didnt get any information about them from the Wiseco.
    I also have question to you with regard to the Wiseco piston. Stock BMW pistons have arrows and those arrows must be pointing towards camshaft drive while installing. I can’t find any marks on the Wiseco piston. Is there a difference which side of the Wiseco piston will point towards camshaft sprockets?

    Mine didn't come either, so I followed BMW stock clearance for rings. I dunno about the pistons for the 4 valve x cyl. but if the valve pockets has the same size overall, I would say you can install in any way...but the gurus about this should chime here.
    Euro M3'87 NogaroSilver/Euro E34 M5 '93/Porsche 993 TT 97' Euro/Porsche 993 Carrera 95' Euro/Skyline R33 GT-R


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    Quote Originally Posted by Maleckis View Post
    Ok. Thanks guy for answers. What about piston rings clearances? Didnt get any information about them from the Wiseco.
    I also have question to you with regard to the Wiseco piston. Stock BMW pistons have arrows and those arrows must be pointing towards camshaft drive while installing. I can’t find any marks on the Wiseco piston. Is there a difference which side of the Wiseco piston will point towards camshaft sprockets?
    Yes theres a difference depending on your piston. There should be a dot showing the front.

    You can see the mark in my pics here:




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    Or as simple as big valve relief goes on the intake side, small one for the exhaust side.

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    that too

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    Quote Originally Posted by StreuB1 View Post
    Or as simple as big valve relief goes on the intake side, small one for the exhaust side.


    I want to be sure. Are valve pockets I marked in the picture for intake valves?
    I don't know why I don't have any arrows or dots on my pistons. I looked them very precisely.
    Could you post here for me your piston rings clearances? I would be appreciate.

  12. #12
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    Quote Originally Posted by Maleckis View Post


    I want to be sure. Are valve pockets I marked in the picture for intake valves?
    I don't know why I don't have any arrows or dots on my pistons. I looked them very precisely.
    Could you post here for me your piston rings clearances? I would be appreciate.
    Yes..larger pockets are the intake side. Ring gap is determined by type, use and cylinder bore diameter.....here ya go.

    http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf

    Don

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    accurateengines@yahoo.com here is a something about end gap that i learned long ago naturally asperated is .004 per inch of bore 4.00 bore is .016 end gap forced induction add aproximately .002 per inch of bore depending on how much boost and piston manufacter Piston to wall as a machinest you add at least .001 clearance to what manufcture of piston calls for. On the end gap we all need to be aware alittle to much is way better than not enough it will break the piston if there is not enough clearance and I have seen it happen same mentality on the piston does anyone know how much a piston grows when heated up to 500 degree I do Guess and email me
    Last edited by Mike Kolbet; 02-17-2010 at 02:25 AM. Reason: forgot to give email adress

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    Thank you for bumping a thread from 2008.

    Seriously - thank you.

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    Quote Originally Posted by 5mall5nail5 View Post
    Thank you for bumping a thread from 2008.

    Seriously - thank you.

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    Jon, where's the snow man?

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    LOL

    I do have a question for the pros; the pistons look like they have a few sharp edges, has anyone experience detonation or "hot spots" with this piston or piston design? Would this be a problem in a high hp FI s50/52?


    Quote Originally Posted by 5mall5nail5 View Post
    Thank you for bumping a thread from 2008.

    Seriously - thank you.

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    Quote Originally Posted by futureroadracer View Post
    LOL

    I do have a question for the pros; the pistons look like they have a few sharp edges, has anyone experience detonation or "hot spots" with this piston or piston design? Would this be a problem in a high hp FI s50/52?
    No they won't be a problem. Burrs will cause a hot spot but a sharp edge won't. Actually the sharp edges have a dramatic effect on fuel atomisation which prevents detonation.

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    Cool, thanks!

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    Quote Originally Posted by 5mall5nail5 View Post
    Thank you for bumping a thread from 2008.

    Seriously - thank you.
    don't be so negative

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    I just read it and save a spot in 2019 so...

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