Run the overhead .... they said !

Discussion in 'Ask An Owner Operator' started by LittleMissCabover, Aug 19, 2014.

  1. LittleMissCabover

    LittleMissCabover Light Load Member

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    I was searching for improved fuel milage. They asked; Have you ever ran the overhead, that'll help ya know. Ran the overhead in May. Milage has dropped from about 5.25 mpg to about 4.50mpg. I'm even trying to be patient but I don't understand "running the overhead'. I had the overhead ran on my old cabover a few years back with the same result. It dropped from about 4.75mpg to a flat 4.00mpg. SO WHATS THE DEAL !!!!
     
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  3. spyder7723

    spyder7723 Road Train Member

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    Very simple, they did it wrong. Either to little clearance or to much. Running the over head, also called running the rack, on today's engines is just setting the valve lash, jake brakes, and fuel injectors. Very easy to do, but most shops never get it right simply cause they rush it, or get it"close enough". Take it back to them and tell them to do it again, on their dime, and do it right. Or take it to another shop.
     
    Last edited: Aug 19, 2014
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  4. Dryver

    Dryver Road Train Member

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    What Spider said, Your mpg's should never be worse after an overhead unless it was done wrong. At the very least I would want the last shop to check it, make sure you get a Sr mechanic and not the pimple head trainee
     
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  5. maggard359

    maggard359 Medium Load Member

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    If you have a mechanical cat or mechanical cummins the fuel mileage will drop just about everytime after an overhead. The problem usually is most dramatic when you have neglected it and let everything run loose for way too long...good for mileage bad for dropping a valve. I see it all the time, don't be too excited give it 10,000 miles it will come back. If it's electronic, they probably mismeasured the injector height.
     
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  6. barroll

    barroll Road Train Member

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    Had the overhead run on my 14L 60 series about 3 months ago, and fuel mileage stayed the same (about 5.5mpg), but it went from burning a gallon of oil every 10,000 miles to burning 4 gallons of oil every 10,000 miles.

    10 weeks, a CAC, radiator, 2/32" off the drives, and a water pump later, mpg jumped up to 6.4mpg, but it's still burning that oil.
     
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  7. spyder7723

    spyder7723 Road Train Member

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    They set the valves to loose. I've never opened up a 14L Detroit, but done my 12.7 lots of times. Takes just over an hour. Very easy. Only specialty tools require is the injector height gauge which can be purchased for a hundred bucks. Everything else is normal tools. Couple wrenches, an Allen wrench set, and feeler gauges. This is absolutely something any one can do. And a prime example of why I say if you are going to own a truck, you better be prepared and willing to get your hands dirty on occasion. Shops do not care if they screw the job up. They still get paid. The worst a mechanic is out when he doesn't do the job right is he has to do it over. That's it.
     
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  8. 201

    201 Road Train Member

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    Hi LMC, where you been? Truckin'? I agree with the others, take it somewhere else. I had the overhead ran on my BC Cummins by someone who went to diesel mechanics school, it ran terrible after. Took it to a shop, the guy asked me, "who did the overhead last?" The first guy was a friend so I didn't say anything to my friend. Ran great after the 2nd time.
     
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  9. barroll

    barroll Road Train Member

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    I ran the overhead on my VT-903 plenty of times (6-8 hour job if you do it right the first time, usually took me about 10 hours with hand tools). I just don't trust myself to crack open an already sick electronic engine since the newest thing I've torn down rolled of the line in the 70's. Suspension, transmission, wheels, doors; sure, I'll crack it open and see what I can do, but load bearing welding and touching an ECM controlled engine are two things I'm not ready for on a big truck.
     
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