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Cummins nt-400-HS overhead settings

Discussion in 'Generators/Gensets' started by HG gentech, Jan 10, 2016.

  1. HG gentech

    HG gentech Member

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    Hi all,

    Can anyone give me some help on overhead settings for this old genset. It has a small cam cummins nt855. I've had differing opinions on what to set the injector travel at for the non top stop style injectors. Sn# is 10429239 cpl#0013.

    Thanks,
    HG tech
     
  2. HG gentech

    HG gentech Member

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    Model is a nt-400-GS not an HS.
     
  3. Shimmy1

    Shimmy1 Senior Member

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    Did you mean to say travel, or are you asking for preload?
     
  4. kshansen

    kshansen Senior Member

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  5. HG gentech

    HG gentech Member

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    I meant travel because I didn't think you could set by preload non top stop injectors.
     
  6. HG gentech

    HG gentech Member

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  7. Truck Shop

    Truck Shop Senior Member

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    Small cam injector non top stop preload 68 inch lbs. Set injectors, crossheads and valves all at one time on that cylinder.

    Big cam injectors are top stops and preload at 6 inch lbs. crossheads and valves are set on one cylinder and injector on another cylinder
     
  8. Shimmy1

    Shimmy1 Senior Member

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    Truck Shop, what's your view on setting Top Stops to 72 in/lbs? My uncle ran several Big Cams to a million miles setting the preload to 72 every 100,000 miles. He feels they run better because you're compensating for lobe and follower wear. Just wondering what your opinion is because from your posts it sounds like you know your way around a Cummins.
     
  9. kshansen

    kshansen Senior Member

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    Well that link does have the spec's for both the torque method and the injector travel method.

    One think I liked about the travel method is you could check them after running to see if they were in spec. Where with the torque method you had to actually readjust every one. Either should work but my personal preference is the travel method, just be sure to determine the rocker box material to get them set right!
     
  10. HG gentech

    HG gentech Member

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    I do have aluminum boxes. I am setting them by travel method. .170 . I let you know how it turns out. These old engines are getting tough to find info on. Cummins have been trying to get specs for me for a week now.

    Thanks for your help.
     
  11. Truck Shop

    Truck Shop Senior Member

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    I have set them both ways and the engines ran about the same. Although setting injectors on a big cam at 72 in lbs does cause the injector to wear a little
    faster. If set at 72 then checked on the base circle method instead of coming in at 6 in lbs, they run around 10 in lbs. That's what I have found.

    The best way to gain more out of a big cam or small cam, Is to back the injector timing from 70 on a big cam to 74. And a small cam from 36 to 40.
    It ends up with a little less throttle response but the rpm hang time between shifts is longer.

    Some years back I worked for a shop that built the long blocks for a diesel machine shop. I suppose I long blocked 90 plus cummins, 40 cats. And
    I don't know how many inframes I've done.

    Truck Shop
     
  12. Truck Shop

    Truck Shop Senior Member

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    I almost forgot, the 400 small cams were known as Magnums by Cummins.