More 425C questions

Discussion in 'Trucks [ Eighteen Wheelers ]' started by bigguns, Aug 11, 2017.

  1. bigguns

    bigguns Road Train Member

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    This engine is stock. I know that I need to change the timing advance and put in steel pistons to get a lot more out of it. A fellow Cat man insisted that by plugging the boost gate hose it would produce up to 35lbs. of boost. So while waiting to unload we did that. I gained 3lbs. of boost. Now backing up, I have turned the AFRC valve screw in the max. The pump screws I have turned 4 full turns. Those 2 things brought it to life with only a short trail of black smoke. The pyrometer did not above 900 degrees. After plugging the waste gate the engine pulled better. The pyrometer dropped about 50 degrees and the black smoke all but disappeared. Pulling an empty trailer it is very quick at low rpms. Loaded it seems to pull the best at 1300 to about 1600. Can I turn the pump screws out any more? Without a dyno, can I turn the screws to adjust the torque curve upward? I don't like to make it pull down at lower revs even thought it does pull well there. @wore out or @swaan if you can get me part numbers for the quad seals in the timing advance I would appreciate it. The Cat people near me are dumbfounded when I ask about these seals. Engine serial number is 3ZJ51828
     
  2. E model Cat man

    E model Cat man Light Load Member

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    You can turn them out another 3-4 turns...your stock nozzles wont allow it to deliver crazy amounts of fuel that would hurt it...the power range deal sounds like a timing weight issue or a governor spring. Should work best from 14-1900rpms really.
     
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  3. noluck

    noluck Road Train Member

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    What is your current max boost? I am not 100%, but I think the c's already have steel top Pistons. You do not want to get the screws out of whack. You need to adjust them equally. Have you bumped the fuel timing any?
     
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  4. E model Cat man

    E model Cat man Light Load Member

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    The C's never came with steeltops if any did it wouldve been an 8pn.
     
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  5. noluck

    noluck Road Train Member

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    I thought they dumped the aluminum after the b's
     
  6. bigguns

    bigguns Road Train Member

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    Nope. Checked on it. Aluminum top pistons. The fuel timing hasn't been changed yet. Max boost was 22 as is correct for this engine. I now get a whopping 25lbs. It is crazy the power it has with so little boost. I did feel the torque should be at higher rpms. I haven't touched the timing advance but I should have it checked out. I need to add thst this truck sat for 6-7 years before I purchased it.
     
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  7. noluck

    noluck Road Train Member

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    What area of the country you in?
     
  8. bigguns

    bigguns Road Train Member

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  9. mtoo

    mtoo Road Train Member

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    If I remember right, my 8PN had steel top

    If I wasn't old and retired ..............I would be looking looking for a mechanical cat.
     
    Last edited: Aug 12, 2017
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