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  1. #1
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    Ym330D

    Default Shaved Head - Need thicker head

    I have a Yanmar 330D tractor that I have recently rebuilt the engine on. I had a local machine shop rebuild a new head (valve job and put old valves on new head). He said that the head was warped and had to shave the head. The engine has a loud fuel knock and does not start very well. It also misses at high RPM. He states that he took no more that 10 Thousandths off. Would/Could this cause the missing, knock, etc?
    Thanks
    Jerry

  2. #2
    Elite Member RobJ's Avatar
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    Default Re: Shaved Head - Need thicker head

    Doubt it. Check the timing. Also what was the original problem? missing hard to start before. How come you had the head done? Does it put out white smoke when starting? Might need a little more info before we go on.

  3. #3
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    Default Re: Shaved Head - Need thicker head

    Jerry,
    It sounds like a fuel issue to me(lack of or wrong timing).. Most diesel heads I have seen are flat, the combustion chamber is in the piston, so machining the head alone shouldnt cause this.(unless your head is different).. It may effect valve clearance, but I believe you'd have a no start if that was the case.

  4. #4
    Super Member Farmwithjunk's Avatar
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    Where do I begin.....

    Default Re: Shaved Head - Need thicker head

    Excuse me for being so presumptuous, but apparently you must be a woman. I derived that by the fact that you need a thicker head. According to my wife, (who's NEVER wrong) Men already have a thick head, so this must mean anyone without that thick head HAS to be a woman.

    Yes, it's been an interesting saturday morning around my house.

    No, I haven't apologized yet. ( But will soon, even though I don't know for what)

    Whatever I did, it musta been good. The dog just got my eggs.

  5. #5
    Veteran Member IH3444's Avatar
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    Default Re: Shaved Head - Need thicker head

    Just going to chime in here. I have some experience with diesels, having built one. The one I built had a stock compression ratio of 22.5 to 1. The factory was very specific about how you measured the head to block arrangment, due to the fact they didn't want the compression ratio changing. You measured the head thickness, and then went to a factory chart to besure that you bought the correct head gasket. They were available in different thicknesses, so that you could match the one you needed to the engine. I also agree that it sounds like you timing maybe a bit advanced, and your injector nozzles may need cleaning. It's also a good idea to get your injectors checked for pressure. Doubt this helps much, but that's what I know about diesel heads. Some shops will heat a head up, then straighten it so that they don't have to flycut it straight. They also know that when the head heats up, it may warp back to where it wants to relax. Gasoline engines are so much more forgiving on this matter. Good Luck! [img]/forums/images/graemlins/smile.gif[/img] I am on the understanding that diesel manufacturers don't like their heads shaved more than .005", more than that, they want them to be straighten. Now that is an art form! What did they do with your original head. Sounds like they transfered your valves to another head. I hope they measured the valve stem taper, and it was well within specs. When a diesel engine goes together, it's usually for a very long time. Why not just get new valves, valve guides, stem seals, and do the entire job up right. By the time you include labor, the parts start look inexpensive. I wish you the best finding out the problem, and hope you don't have to pull the head again. [img]/forums/images/graemlins/confused.gif[/img] Diesels are also concerned with how deep the seats are cut, and the valves sunk into the head. I'm sure that the shop that did the work will reassure you that they checked that also.

  6. #6
    Platinum Member
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    Jinma JM354

    Default Re: Shaved Head - Need thicker head

    This more of another question. Would taking a compression test resolve some of the higher compression issues. I would agree to check pump timing. I had this problem recently and timing the pump to engine resolved it. Also if gasoline got mixed in the fuel some how, could this be something you have? Good luck. bjr

  7. #7
    Super Member Farmwithjunk's Avatar
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    Default Re: Shaved Head - Need thicker head

    But seriously folks, If there was a valve job done, that would (should?) set the valves a scant bit deeper. That would negate some (all?) of the loss of volume when head was cut. A bunch of variables there, but something to consider.

  8. #8
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    Default Re: Shaved Head - Need thicker head

    Thanks for the responses. Iíll answer the questions as best as I can
    Rob,
    I had to replace the head (original cracked). I took the old head and the new one to a machine shop to get the valves ground and placed on the new head. They told me that the head needed shaved. The business that I purchased it from told me that it had been sitting on their shelf for a very long time and they thought it was new. The guy at the shop said that it looked good (except for being slightly warped) but did appear to have been on an engine.
    The engine ran pretty well for a couple hours, but missed at high RPMs. The last time I started it, it put out some white smoke Ė ran pretty rough, then would not start. It still does not start. I now have it at a local kubota shop. I asked them to check the compression and determine if the problem is still related to the injection pump. Iíve had the tractor to another shop twice where they have supposedly rebuilt the injection pump but they do not want to do anything after around $1,300 (Thereís many questions I could ask about what do about that Ė another day).

    Farmwithjunk,
    No, Iím not a women but I have been accused of having a thick head. Your though about the valves setting deeper is interesting.
    Anyone else have a thought on this?

    Iíll post an update when I hear from the Kubota shop.

  9. #9
    Elite Member RobJ's Avatar
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    Default Re: Shaved Head - Need thicker head

    I would think you have plenty of extra valve relief if they only took off a few thousands.

    White smoke usually means water in the combustion chamber. Now this could cause some of the described problems. And since it started all of a sudden it would describe either a head gasket failure or the engine warming up and allowing water through a crack. Not knowing where the new head came from could raise a question. It is possible you unknowingly replaced a bad head with a bad head. A look at the water in the radiator might give you an indication if you have a blown head gasket.

    Good Luck and I hope you get it resolved quickly.
    Rob

  10. #10
    Veteran Member
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    YM2000

    Default Re: Shaved Head - Need thicker head

    </font><font color="blue" class="small">( Your though about the valves setting deeper is interesting.
    Anyone else have a thought on this?

    Iíll post an update when I hear from the kubota shop.
    )</font>

    I tend to agree that the deeper valve set would negate the head machining.. Now, I just noticed the issue of white smoke.. did you have the same power before the reair as after? I wonder if you could have the wrong head gasket? Lower compression would cause white smoke and a lack of power, but probably not the no start unless it was quite cold.. Just a thought..Maybe the gasket is too thick.

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