Injector push tube screw; small cam vs. big cam 1-3 vs. big cam 4

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Feb 19, 2024.

  1. mile marker 27

    mile marker 27 Road Train Member

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    IMG_5096.jpeg IMG_5097.jpeg Engine is a small cam, rocker boxes came off a bc1, so that jakes can be used. Two of the boxes had screws with the 7/16” head and the other box had the flat screwdriver style. The flat screw driver style was swapped with screws from a bc4 and they have a 9/16” head and shorter. The reason they were swapped, was to get an accurate reading of 6’lbs/72”lbs on the injector setting. When setting the fuel, while running the OH the fuel screw seemed to bottom out on the jam nut before we could the the desired tension. All the others, with the 7/16” head did fine. I/we weren’t aware that these may not interchange. Here’s a pic of all three and the 9/16” head screws, from the the bc4 are shorter. Cummins guru’s please enlighten me.
     
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  3. mile marker 27

    mile marker 27 Road Train Member

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    So, it’s my belief that you can use small cam , push tube fuel screws in only small cams but you can you either, in a big cam. I was continuing to have issues with number 2 cylinder, being over fueled or low compression. image000000.jpeg
    I changed the front rocker box, because it felt like #2 cylinder rocker shaft had a touch of gaulding and wasn’t as smooth as #1. Removed head and took it back to the machine shop. Said he removed valves, checked springs, guides, ground the valves. He did the heads originally and swore there was nothing wrong with the head or his work from his original work. He’s the kind, if he found something wrong the second time, he probably wouldn’t admit he missed something or made a mistake. So, that said, I’ll never really know if the head was the issue. The original issue was excessive white smoke, popping sound from 1600-1800rpm and excessive fuel at #2. Put air pressure at injector cup to see if any air was getting into crankcase but no signs. Checked injector and put new o-rings on. Now, I’m at these fuel push tube screws.
     
  4. Nss

    Nss Light Load Member

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    Screw driver style is what should be used. Why do you need different rocker boxes? Only needs the hollow center screw to allow oil to pass to jake assembly and different exhaust valve bridge
     
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  5. Nss

    Nss Light Load Member

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    Also would need 6 of the correct screws in the injector rocker. That depends on the jake model
     
  6. mile marker 27

    mile marker 27 Road Train Member

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    I had to change rocker boxes initially because I was adding jakes and the existing boxes had the wide exhaust rocker arms. I didn’t want to grind them all down so I used some donor boxes, from a bc1.
     
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