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Cylinder ovality/ out of round??

Discussion in 'Diesel Tech / 24 volts' started by mac, Aug 15, 2006.

  1. mac

    mac Crew Member

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    Can anybody tell me the max tolerance for out of round (diff btwn axis/thrust) in the cylinders of a diesel? In this case, as you know, a 1HDT but that shouldn't make a diff.

    Thanks,
    Peter
     
  2. nickw

    nickw

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    I am guessing no more than they can over bore it too.
    10 thou, 20 thou....
     
  3. crushers

    crushers post ho SILVER Star

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    deffinately get a machine shop to mic the engine. might as well get the entie engine refreshed while you are in there...
    the thing is you don't know whee some metal particles could be lurking waitng for a new bearing to eat up...
     
  4. mac

    mac Crew Member

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    I'll be dropping it to be mic'd. I've mic'd it myself but my inside measuring tool is not the dial type and it makes getting a super accurate reading (talking .0005")very difficult. Okay for a gasser but not accurate enough for a diesel compression ratio. I've determined the out of round on each cylinder to be less than .001" except #4, which is just over .001". I was initially told by Geoff Walsh that anything more than .0005" was unacceptable on any diesel. At that point I thought, oh well, even though the cylinder bore is well within spec, the ovality is going to lead to punching out the block. And then...Late last night they sent me another email saying that they had checked with two reputable machine shops down under and had gotten the same response- .001"-.0015 was perfectly acceptable. Here's their explanation:
    As the 1HDT is considered a light duty diesel in that it doesn't have cylinder liners, it is expected that it will measure distorted without the head on- and the maximum distortion allowable are the figures they gave me. What I can't understand is - why doesn't the freakin' expensive FSM say ANYTHING about ovality of the cylinders? Even though it instructs you to measure @ axis & thrust points, it only gives max wear #'s in general. There is no comparison of the two figures.
    Well off to the machine shop! I've got to find a decent one first!

    Peter
     
  5. BC Cruiser

    BC Cruiser

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    Ok, just cleaned off the dust and cracked open one of my diesel textbooks from school. They spec in the book .005" (.127 mm). So you should be measuring at the top of the cylinder, about an inch down from the top so your not measuring on the cylinder ridge. And then the same at the bottom of the cylinder. Now this is out of book for large diesels like cat, so your measurement might be smaller.
     
  6. wussyPup

    wussyPup just another ex-VI Cruiser

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    OK, I'm feeling a little brave today, and a lot dumber than usual...

    Why would an out-of-round measure matter in a non-rotating application like pistons and cylinders? Aren't the max/min tolerances the important measures? As long as the clearances are within spec, (no binding, no slop) can't an oval piston work fine in an oval cylinder?

    Thanks,
    -Steve
     
  7. mac

    mac Crew Member

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    Measurement is done at 6 locations in each cylinder. Two at the top 10mm from head surface(thrust and axis), two in middle(thrust and axis) and two at the bottom(thrust and axis). The wear is , of course mostly to be found at the top of the cylinder and this where the greatest difference between thrust and axis measurements will be found.
    While that # makes me feel better, 5 thou seems like a big varriance for these little cylinders. Land Rover specs .0016" for ovlality on their 3lTD.
    Oh, and thanks for lookin' for me. The more heads the better!

    Cheers,
    Peter
     
  8. mac

    mac Crew Member

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    Yes it can, but my pistons aren't oval. It actually has more to do w/ the rings , not the piston. The rings provide the sealing surface and they will have a hard time sealing in 485+PSI if the bore is not round throughout the duration of the stroke.
    Thanks for your input,
    Peter
     
  9. BC Cruiser

    BC Cruiser

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    Yes your right it's measured in three different spots. Its really easy to measure if you have a telescoping snap gauge and a mic, you can do it. Also one cool fact I just remembered, did you know that pistons are infact elliptical in shape when cold. This allows for thermal expansion.
     
  10. mac

    mac Crew Member

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    I wish I had a telescoping snap guage that attached to a dial indicator but I don't. I have the type of inside measuring tool that screws in or out to meet the diameter and then the meas. is read off of the part of the tool that spans the bore. I actually have to get it into position and then read it while I hold my breath so as to not move one hair, and look down into the bore. As I said, a gasser has lots of margin for error but the tolerances on a diesel are just too close to take a chance w/ a sketchy measurement.
    And yes, some pistons are eliptical- I'm not sure about the 1HDT's. I'll check.

    Peter
     
  11. light_duty

    light_duty

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    Peter, did you see that guy selling brand new 1HD-T short blocks from Japan? I think he said $4000 shipped, 5-6 days air freight from Japan. It was a thread in the vendor section.

    Just a thought.
     
  12. mac

    mac Crew Member

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    Robin, thank you very much for that. I've contacted him. He's actually local to me in Vancouver and we're going to talk tomorrow. It sounds promising!

    Thanks again,
    Peter


     
  13. mac

    mac Crew Member

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    Update

    Well, so much for rebuilding. Anyone need a 1hdt block, rods & pistons? I'm going for the factory new shortblock. Thanks to Rob from RADD and James from JDM for all of your help so far. Thanks also to you Light_Duty for puttin' me on to the ad. Now the waiting game begins- oh well I have a head to clean up! Oh yeah, and a 62 diesel conversion that I'm still working on... I've been neglecting her...

    Cheers for now,
    Peter
     
  14. nickw

    nickw

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    Hello Peter,

    What does a new factory short block come with (turbo, starter, alt etc..?), and how long of wait game?

    I might want to pick up a few spare parts.
    How is your injection pump, injectors etc.....
    Might be worth wihile me having a spares around.
    I have had some bad luck, and I would like to have some parts around that I have not broke yet.
    Better to get them cheaper when I don't need them, rather than for alot when I do.

    Maybe even your exhuast manifold?
    Who knows. Guess it depends what with the new engine.
    Maybe PM me.

    Thanks,
    Nick
     
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