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  1. #1
    Member
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    yanmar 336D

    Default Engine Piston Height

    Does anyone know how far up in the liner the piston should come up on a 3t84 or 3t90 yanmar engine?
    I think mine are coming up to high. .019 above the cylinder liner.

  2. #2
    Elite Member
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    gilmer tx
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    Bobcat CT235

    Default Re: Engine Piston Height

    I don't know what you could do to change the height the piston is coming up. However the sleeve is another question. The sleeve is to be from .0002 to .003" above the block. Does yours fall in that range?

    Another interesting bit of information is the block bores should be marked A, B, or C. Liners will also be marked A, B, or C. This mark should be on the camshaft side of the block. A is larger than B, B larger than C. When I say larger I am referring to block bore deminsions. Nothing to do with your question but I had not seen this before. So you guys changing liners need to remember that to assure getting the correct liners for your engines. Woe is me, my YM2002D has no liners.

    Let me clarify a little more. This information is out of a service manual for a YM276, engine 3T84HA.
    Last edited by winston1; 03-27-2012 at 01:22 PM.

  3. #3
    Elite Member Car Doc's Avatar
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    YM3810D Yanmar

    Default Re: Engine Piston Height

    My 336 book which is incorrectly listing the 3t90 in all its specs (rather than 3t84) says liner above deck is .003-.006".

    I believe the 2 are interchangeable in that spec from what I saw in mine and my pistons were above the liners also. I didn't measure them but they were above and my liners were equally set at .005-.006" which I did measure.

    My opinion is this-if the liner is at that height and it ran before it has to be ok thats my common sense answer. Now thats unless someone has line bored the living heck out of the main bearing bores and thats highly unlikely it would even be measurable at the deck.

    Look at it like this-The head gasket is another probably .035- .045" guessing compressed so there is clearance. I know .019" isn't an interference concern with the head deck anyway. Maybe the pre-chambers depending on whats been done to the head however. fwtw
    Yanmar YM3810D, LT duty 3pt hoe, 6' KK2 tiller, 6' KK box blade, 6 1/2' KK disc, 5' Howse bush hog, 5' Howse back blade, 9" Yellow PHD, 3 Husky chain saws 346XP NE, 359, 372XP. 07 HD Heritage Softail, Crack injectors, check compression, take 2 beers and call me. "Hey you didn't build that."

  4. #4
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    yanmar 336D

    Default Re: Engine Piston Height

    Thank you for the come back. Liner height is no problem. I guess I need to measure the how far the pre combustion chamber is below the head surface.

  5. #5
    Elite Member Car Doc's Avatar
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    YM3810D Yanmar

    Default Re: Engine Piston Height

    Quote Originally Posted by dalehowe View Post
    Thank you for the come back. Liner height is no problem. I guess I need to measure the how far the pre combustion chamber is below the head surface.
    Welcome. The reason I mentioned the pre-chambers is my head was warped pretty bad it measured .009" and they took the minimum off (no idea what that was 10-12 thou probably) they could because I wanted it that way.

    I had concerns with the close proximity of the rest of the combustion chamber though (you will see what I mean) and didn't want to go about assembling and claying the pistons etc.

    So I added an extra copper shim .020" approx under each of the chambers to take up that that was milled off and it worked great. The specs I remember finding said NOT to mill the head but I rarely pay attention if I have a solution.
    Yanmar YM3810D, LT duty 3pt hoe, 6' KK2 tiller, 6' KK box blade, 6 1/2' KK disc, 5' Howse bush hog, 5' Howse back blade, 9" Yellow PHD, 3 Husky chain saws 346XP NE, 359, 372XP. 07 HD Heritage Softail, Crack injectors, check compression, take 2 beers and call me. "Hey you didn't build that."

  6. #6
    Member
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    yanmar 336D

    Default Re: Engine Piston Height

    Thank you Car Doc. That will help conserably Dale

  7. #7
    Elite Member Car Doc's Avatar
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    YM3810D Yanmar

    Default Re: Engine Piston Height

    Yanmar YM3810D, LT duty 3pt hoe, 6' KK2 tiller, 6' KK box blade, 6 1/2' KK disc, 5' Howse bush hog, 5' Howse back blade, 9" Yellow PHD, 3 Husky chain saws 346XP NE, 359, 372XP. 07 HD Heritage Softail, Crack injectors, check compression, take 2 beers and call me. "Hey you didn't build that."

  8. #8
    Platinum Member Domush's Avatar
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    1981 Yanmar 336D

    Default Re: Engine Piston Height

    I was just wondering about this exact same scenario on my 336. I love this forum.
    It is the mark of an educated mind to be able to entertain a thought without accepting it. ― Aristotle

    Yanmar 1981 YM336D

    From this . . . . To this
    ...

    Check out the full restoration project: Part 1 - Part 2 - Part 3 . . . . Adding gauges? How-to

  9. #9
    Member
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    yanmar 336D

    Default Re: Engine Piston Height

    Hi Domush: I never did get a very good come back to my question. Dale

  10. #10
    Platinum Member Domush's Avatar
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    1981 Yanmar 336D

    Default Re: Engine Piston Height

    Well, if it helps you any, my pistons come up .018"-.019" above the deck (not the liners, as they are not all the same on mine).

    So, if you compare yours to mine, they are normal. Though I haven't found much normal about mine, hehe
    It is the mark of an educated mind to be able to entertain a thought without accepting it. ― Aristotle

    Yanmar 1981 YM336D

    From this . . . . To this
    ...

    Check out the full restoration project: Part 1 - Part 2 - Part 3 . . . . Adding gauges? How-to

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