400 big cam advice.

Discussion in 'Trucks [ Eighteen Wheelers ]' started by MrPlow93, Nov 13, 2015.

  1. flattop

    flattop Bobtail Member

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    This is why I stay away from here, I won't argue it's a waste of time, you are right there is no such thing as a 444 1211 you caught me in a lie....
     
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  3. SmokinCAT

    SmokinCAT Road Train Member

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    Oct 20, 2010
    Hillsboro, OH./ Adrian, MI
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    There are a lot of things I have noticed in the research I have been doing. The timing is very much all over the place, and I think that the later engines that they were trying to get to "lug" seem to be the ones that have the more retarded timing, yet the injectors flow similar.

    The generator drive engines I mentioned have high flow injectors comparable to what was used in the NTC-475 truck engine, these are timed around .120" or a little less, the MVT was timed at .125" in retard, but the generator engines run at a constant 1800rpm.

    While looking at these timing numbers one should note that there are three different injector travels for the 855 Big cam, .224", .242", and .266" so timing may be adjusted to be proportionate to overall travel.

    The ones that really throw me off are the mechanical N14s which really are just and even more updated big cam, these engines have the same injector travel but timing is quite retarded, the N14-430 is timed at .176", I would say some of this may have to do with air to air, as cat also took their timing the same way when switching to air to air. Cummins may have also set the timing this way to allow lower rpm heavy fueling to try and lower the powerband.

    Retarded timing does not make more power, what it does is allow you to make power at a lower rpm which is where the burnt up pistons come from.

    I do not hear much about the older engines, I know piston compression options were not much with the earlier engine, now though there are plenty to choose from and lower compression with the retarded timing may help longevity of head gaskets by trying to keep cylinder pressures in check.

    I am not sure what your question is in regards to the fuel pressure?
     
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  4. SmokinCAT

    SmokinCAT Road Train Member

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    Lie, no. Misinformation, yes.
     
  5. Simp5782

    Simp5782 Bobtail Member

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    May 19, 2019
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    What about using the intake manifold from the NHC250s that were non turbo. They have a 5 inch take on them. Or are the runners not big enough?
     

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  6. SmokinCAT

    SmokinCAT Road Train Member

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    I wouldn’t use one of those just because the amount of adapting that would need to be done.

    N14 parts are common and that makes it easier to find parts that take less adaptation than a 5” inlet would.
     
  7. Simp5782

    Simp5782 Bobtail Member

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    Silicone intakes makes a hose to go from 5in to 4in. Seemed like a simple and easy install in my ex military truck. Just didnt know if there was a difference in flow rating in it vs the n14 intake. Screenshot_20190519-114826_Gallery.jpg Screenshot_20190519-114833_Gallery.jpg Screenshot_20190519-114826_Gallery.jpg Screenshot_20190519-114833_Gallery.jpg
     

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  8. Bias_racing

    Bias_racing Light Load Member

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    So..since the last post was in 19 im going to presume its alright to high jack? If not I'll start another.

    Just bought a train with a cummins. Cpl676 so that appears to be a bc3 nt855 according to quick serve. My motor appears to be weeping oil from the head gaskets as well. My mech wants to change the head gaskets. According to this thread it should be left alone, is that the consensus?

    She drove from Minnesota to texas just fine. She smokes like a train on start up and a little haze after shes warm.
     
  9. BoxCarKidd

    BoxCarKidd Road Train Member

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    If it has a lot of blow by gaskets would probably only be a temperary repair. Make sure you do not have any leaks coming down from higher up. Rocker shaft o-rings and such. Blocks of that age tend to have a lot of fretting. Sometimes they need to be decked. If it is a slight head gasket leak I would run it.
     
  10. Bias_racing

    Bias_racing Light Load Member

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    Aug 4, 2019
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    No blow by that i can see. Run it with the oil xap off and it has no blow by at all has a 13 speed trans but its like under drive not over. Technically I'd say its an 8 speed. Truck had a hoist and pto, "special service truck" it only drove little less than a mile a day so its low miles, but has plenty of hours.
     
  11. Catmando

    Catmando Medium Load Member

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    I reresurrected this thread needing opinions .. 1st off I'am not a Cummins Guru by any means .. but looking at a truck with a BC3...400 its weeping a little coolant from the #2 head gasket..my gut feeling says it needs to have head gaskets .. the owner says that's common .. I read this thread looking for info but the issue in this thread was oil related not coolant.. I know Cummins like to seep some oil but I didn't know if coolant was a issue also ?
    And thoughts and opinions are welcome
     
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