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400 Big Cam / N14

Discussion in 'Trucks' started by dieseldog5.9, Feb 11, 2018.

  1. dieseldog5.9

    dieseldog5.9 Well-Known Member

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    So I have a 400 big cam, starts in the cold like a 400, smokes like a locamotive if cold, wicked touchy mid throttle, truck jerks bad at times mid throttle, you have to drive full throttle or no throttle to drive smoothly, loaded it's a little better. If I plug the truck in at night I can prevent the cold smoke, and pulls hard loaded, and the jake could hold back a locamotive.

    So here's the question, if I send the injection pump out, it may help the jerky throttle, but truck will still smoke cold.

    Option 2- pull the engine buy an N14, throw enough money at it and I can have 550 smoke free hp. Takes a lot of cheddar to make this option happen.

    Option 3- buy a junk N14 with a bad crank or block, swap the parts, using my block, crank, rods, swap Pistons, and fuel system parts, cam. But is crank and block the same? Less cheddar more sweat equity.

    Thoughts?
     
  2. Junkyard

    Junkyard Senior Member

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    What CPL is your current motor? Cummins used a couple different ways to manage the timing. I've driven a few that acted like yours does and with some tinkering those issues were addressed.

    How much of the history do you know? Last time overhead was run? Mileage on motor itself, injectors etc?
     
  3. farmerlund

    farmerlund Senior Member

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    I have owned one that runs exactly like you describe for 26 years. Over the years I have replaced heads, injectors, fuel pump. ran the rack occasionally. nothing ever changed the way it ran. or smoked after a cold start. I never understood why it smoked raw fuel so bad if it was under 45-50 degrees. it always started quick and pulled very good. I never had any sparrows living in the building I kept it in. LOL

    I did get the throttle a bit better by reworking the linkage so it had a longer throw on the pump. witch slowed down the movement. (old dirt track trick) Made it less jumpy.
     
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  4. RZucker

    RZucker Senior Member

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    Does this engine have oil pressure operated step timing control? If so the STC tubes may have blown out of the injector adaptors, once they get sprung out of place they leak off the STC signal and lose the injector timing advance at idle. The result is lots of eye burning white smoke and a drastic drop in hot oil pressure at idle.
     
  5. Tenwheeler

    Tenwheeler Well-Known Member

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    The later BCIII 400's did the smoke thing brand new. I was told if was a compromise for what they called emissions back then. It is related to camshaft timing and probably why the STC system evolved. That is just the nature of the beast.
    As far as the surging at mid throttle it sounds to me like a governor issue. Replacing a solid rod with a cable to the pedal was great in some trucks. However surging from that is expected more at slower speeds.
    The last one of those running where I worked was heavy haul and a bit hot. If it was started up, winter time cold, in the shop we feared someone would call the fire department. It would roll two feet of coal out the top of all the doors. After warmed up it cleared up and had perfect manners.
     
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  6. Truck Shop

    Truck Shop Senior Member

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    What position is the throttle lever on the pump? It can't be forward of the break over point or past 90* or it will cause a very touchy throttle. And what series is the engine II, III, IV, NBCIV
    or NT 88. The NBCIV, is STC injector and those do not set to original factory Specs. As far as smoke part of that is compression ration on big cams Although the first BCIV was higher compression
    than any in that series and would be a BCIV CPL of 676 mainly. Check the throttle shaft for up and down play, When was the last time that pump had any attention? Is that pump still sealed?

    Here is a link to procedure for setting STC injectors if it has them.

    http://www.chathamfuel.com/generic....Tech Tips - NT/N14 OBC Overhead Set Procedure

    Truck Shop
     
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  7. Truck Shop

    Truck Shop Senior Member

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    You can make that Big Cam run. I had a BCIII CPL 625 that I installed double ni resist pistons/liners and heads from CPL 676. Had custom built 8 orifice injectors with a
    KTA 525 1 inch gear pump and fed fuel in both ends. I used the cam from CPL 676 because it has slightly more lift. Pulse manifold with a HT3B turbo. Timed the injectors
    at 74-little less throttle response but more hang time between shifts. The pump was re-calibrated to match the rest of the components. It would run. But the secret is
    in the injectors if they don't have the flow you don't have the power plus it will cause higher rail pressure. IMO.

    Truck Shop
     
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  8. dieseldog5.9

    dieseldog5.9 Well-Known Member

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    Great responses, I bought the truck last spring, it is an 81 western star. I converted the front axle from wedge to s-cam brakes and hub pilot aluminum wheels. Rebuilt the power steering gear, and removed 10miles of homeowner wiring. I replaced the ball studs on the linkage hoping to help the issue. Pretty sure it is a big cam 3, and don't think it is an stc engine, thought they came out later, considered pulling parts from an stc 444, to help the smoking cold. I will have to look tomorrow for the CPL. The injection pump shop I use think there may be a governor issue causing the jerkiness, he said he has been fighting with smokey 400's his entire career and suggested also running the overhead, but nature of the beast. I read about 20 pages from Pittsburg power on building horsepower in a big cam, but when I called them I felt like I was bothering them. Truck is pretty cool short cab long hood and a big cam 3.
     
  9. Tenwheeler

    Tenwheeler Well-Known Member

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    81 should be a BC I or BC II. They had an aluminum oil pan and single spin on filter. All of the ones were I worked had a LF750 by-pass filter also. Big Cam III has twin spin on filters and a stamped steel pan. Keep those STC parts away from it. Cam changes and such make it non compatible. Some people put Cat charge air coolers and radiators in front of them. If you do anything much to it it needs a pyrometer. An N14 would need one of those also.
     
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  10. td25c

    td25c Senior Member

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    Sounds like 449 CPL . They would white smoke when cold . Slow time setup on the cam timing .

    Start pretty decent & made good power , just smoke up the valley until it warms up .:)

    Have one in a dozer .
     
  11. dieseldog5.9

    dieseldog5.9 Well-Known Member

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    Yes the original engine was a 300 with a 9 speed, at some point the 300 was pulled and a 400 installed with a 15 speed, the oil pan is a stamped pan, so big cam 3, i made sure when i bought the truck it had large radiator hoses and wasnt low flow. The snow on the hood is almost level with the top of the cab, walking on the snow i look directly into the windows yesterday. I will work on getting the hood open this afternoon and get the CPL. I plug the truck in because i am afraid the fire department will show up cause they think my barn is on fire, and yes light grey smoke, lots of it, looks like a brush fire with a balsam tree on it.
     
  12. Tenwheeler

    Tenwheeler Well-Known Member

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    We considered that no smoke after the 25 head herd of 8V-71's left each morning.
     
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  13. Truck Shop

    Truck Shop Senior Member

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    Given all the horse power and torque ranges in Cummins Big Cam engines here are the number of CPL's for each series

    BCI---26 different CPL numbers from 205 to 661
    BCII---33 different CPL numbers from 329 to 543
    BCIII---37 different CPL numbers from 530 to 1411
    BCIV---35 different CPL numbers from 642 to 1352

    And every one is a smoker.

    Truck Shop
     
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  14. Junkyard

    Junkyard Senior Member

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    I wish you'd have sent that herd my way! I don't know what it is about those old Detroits but I sure do like them.
     
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  15. DoyleX

    DoyleX Senior Member

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    The reason it smokes has everything to do with the timing and fuel rate of the injectors. All pt pumped engines were fixed time and smoked white at cold start and after cyl temps come down at long idle times. That is the way they are.

    Sick of it? Go STC. Sending you injectors in to get cleaned and reflowed to stock might help.
    No fancy tools to work on a cummins, just a butter knife and pliers. If your handy a good fuel shop could go through your pump and injectors for a grand if you pull em.
     
  16. DMiller

    DMiller Senior Member

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    400's of ANY CPL were smokers, decompressed where the pistons have no valve reliefs as they do not get that far up, took boost to get the fuel to burn.

    I missed out on the STC engines(luckily) heard they were very much the way described much like a two stroke with an expansion chamber either on the pipe or off and harsh getting there either way.
     
  17. DoyleX

    DoyleX Senior Member

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    Put a N14 turbo on a 855 and now you have a electric motor.
     
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  18. Truck Shop

    Truck Shop Senior Member

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    I guess the big question is what are your plans for this truck? Remember N14's take a air charge cooler. Cheaper to repair the engine you have and more practical. The BCIII was the best of the big cams,
    the IV, NBIV, NT88 and 444 were all problem childs that damn near sent Cummins to the brink.
    Those were all experiments that didn't work very well. And really what saved them was the N14
    electronic.

    Truck Shop
     
    Last edited: Feb 13, 2018
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  19. RZucker

    RZucker Senior Member

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    MVT on the 444 was a joke, STC on the others had its issues, but did ok when it was working and did reduce idle smoke quite well, as I recall even the N-14 mechanical used STC.
     
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  20. dieseldog5.9

    dieseldog5.9 Well-Known Member

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