Need Advice on Cummins in 1971 Autocar A64B

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by apsencik, Oct 22, 2019.

  1. apsencik

    apsencik Bobtail Member

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    Oct 22, 2019
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    Im trying to figure out whats exactly going on with the engine in this newly acquired truck of mine. Engine runs great and has 10K on overhaul but is severely under powered. I was going to replace with a BC400 or a B model CAT but this engine runs so well that im hesitant till it blows. I cant really get anyone (even Cummins) to tell me exactly what i have here. I do know it is a NHC250, but the turbo throws me off. Ive had some say its an add on. Ive had some say its a 270 or 290. Some say it does or doesnt have cooler nozzles. If I can make this engine pull a 48' equipment trailer loaded with no more than 30K#'s than ill keep it for a while. But the way it is, it is almost unbearable. What can be done to this engine to make it more powerful without sacrificing too much reliability? Thanks.
     

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  2. 062

    062 Road Train Member

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  3. BoxCarKidd

    BoxCarKidd Road Train Member

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    A lot of things can change in over 45 years. Please post a picture of the fuel pump plus some of the right side above the oil pan.
    Look at the normal low power items like air filter and such. Then connect a hose to the side of the fuel solenoid. Hang a pressure on the mirror. What does it read while driving under load?
     
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  4. DougA

    DougA Road Train Member

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    Good advice,like he says,check simple stuff first. All filters. Should run your rack,and make sure all that's correct. Check the snap pressure at the solenoid,that will tell a lot about the fuel system settings,and condition. If that's the original tag,turbo is an add on. Does the truck have a pyrometer or a boost gauge? As far as getting a little more power,it can be done fairly simple with a fuel button change,or open the throttle shaft a little,if your turbo is working and making boost. But you need to know that everything else is correct,before doing these things.
    Good luck.
     
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  5. x1Heavy

    x1Heavy Road Train Member

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    The engine itself will only give you a certain amount and anything heavier put on it will just make it work too much.

    We had a few of those autocars in the one plant at little rock and when I take one of them out with 12 yards in the drum upgrade to the 630 off it's ramp it's not fast at all. Just have to wait for it to come up enough to upshift and hope you have enough to stay in the next gear. Most jobs in the area you never really have it opened up and rolling anyway due to all the hills. alot of patience as it wound out the tach.

    Just a thought.
     
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  6. DougA

    DougA Road Train Member

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    Yes,but it's still an 855 cid engine. Timing CPL will restrict power somewhat,as will old design technology like manifolds,and no piston coolers,etc.,but if it's healthy,everything adjusted correctly,set up a little,it will have no problems with 30k payloads. We used to go across country,73280 with less. My 69 IH CO4070A standard equipment engine was a NHC 250.
    It's not going to go up Donner with the big strappers,but it has the cid,and torque do respectable work.
     
  7. BoxCarKidd

    BoxCarKidd Road Train Member

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    Little Rock memories. Duck hunting was good at the uncles place as a child. Traffic between there and Memphis maybe very bad. Having you car repaired at Mark McLarty can be horrible!
     
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  8. x1Heavy

    x1Heavy Road Train Member

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    We quit using dealership, they qouted 115 dollars in Searcy to look at a jammed cig lighter vs cell charger. Another shop in the town took care of it gratis. And our cost was a replacement charger.

    I have a very old tahoe, just recently had a generic shop bolt in a high line power steering line for a few dollars. It was fortunate the powersteering box did not take too much damage. As long there is parts you can have a shade tree fix it. VS today's overcomputerized crap.
     
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