4MG Rebuild

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

  1. Oxbow

    Oxbow Road Train Member

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    Thanks @pushbroom, and good to see you!
     
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  3. RGN

    RGN Road Train Member

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    Easy Peasy if you've got the lifting equipment, which you do. I'd suggest buzzing together a spreader bar for the pick.

    04_45_19.jpeg

    04_46_27.jpeg
     
  4. RGN

    RGN Road Train Member

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    WT......F?
    Ok, that's just....wow.
     
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  5. Oxbow

    Oxbow Road Train Member

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    And then picking from underneath I gather?
     
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  6. RGN

    RGN Road Train Member

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    Yep. Takes a little field engineering to not squish anything. Some Coors and a couple buddies is a BIG help.
     
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  7. Last Call

    Last Call Road Train Member

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    When you get ready to do that dial me up @Oxbow 1000002857.jpeg 1000002858.jpeg
     
    Last edited: Feb 20, 2024
  8. IH Truck Guy

    IH Truck Guy Road Train Member

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    Only thing I can figure, is @tramm01 is still upset with you for beating him on the links.
    So he's trying to mess with your head .:D:D:eek:
     
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  9. wore out

    wore out Numbered Classic

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    CHASIN THE DEVIL'S HERD
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    If it were me I would really think about doing the lower bores. I’d pull a draw file across the top and counterbore it if nothing else. Being a 4MG narrow rod motor I’d go back with a 160-1131 piston and either a 3425 nozzle which is what the 460 PEEC’s ran. It is 14.5 to 1 and a stronger piston but still aluminum. Do not run the 3421 nozzle the bowls are different from the 7FB 14.5 to 1 and will not match. I know you’ve run a 7W-7031 nozzle or 8785 and had smoke however the 8785 is a match to this piston and is run in several industrial applications up to 580HP. Leave your timing stock. The specs on this setup is 14 degrees. The 4MG is 18 and works really well with this setup.


    I have run several mechanicals several ways. The factory 460 set up with a 4MG pump was as good as it gets. Plenty of power and clean as a plate when Doc is through with it.


    With only a 100k on the cracked motor out of frame if the cylinders looked good I would be tempted to pull them with the expansion plug puller and o ring them and reuse. I hate to see good stuff go to waist but I also understand it’s out and no one wants to go back in one. Another way to see it is new doesn’t guarantee better and if these made it a 100k then they are proven lol.

    I would go through the pump for sure, make sure the stub shaft and bushings up front are good and reuse the 6 point head bolts replacing any that are pitted. Maybe I’m nuts but they torque easier than the newer 12 point bolts. You’ll need an extra deep socket for the Jake studs on the rocker shafts if you go back with Jake’s. Really look at your bridges as well as your rocker arm tips for wear. Check your rocker shafts for wear as well.

    I wouldn’t mind a bit when you get to that point to come help you a few days with the parts you’re not exactly comfortable with. Any tools you need just let us know I can have my boy run by the shop and get it then my wife ship it to you. It’s not like I use that stuff even monthly anymore. With your attention to detail it’s certainly well within your capabilities and a guaranteed good outcome
     
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  10. broke down plumber

    broke down plumber Medium Load Member

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    I would hate to see the bill if this all was hired out $$$$$$
     
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  11. wore out

    wore out Numbered Classic

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    For what it’s worth I started with a 3ZJ block with a broken crank. By time I put the block back square top and bottom, new head, rocker shafts, several rocker arms, bridges, ARP head studs except in the long ones that go through the rocker shaft pedestal’s, nozzles (new not reman), exhaust manifold, both turbos and plumbing, balancer, cam, lifters, had a crank at home I just had checked but had to change gear so it would work, cylinder packs, and new plungers and barrels in the pump as well as bushings, weights races and springs I had 35k in my ol B. I guess in technical terms it could be considered a C though the pump is technically off a B though some will argue that point. It’s also the exact profile of the 4MG pump but uses the dual scroll plungers and barrels. Patience was hard to find, I’ve handed several a bill on a 35k engine but never myself one. Getting it dialed wasn’t a quick simple deal as mine is sorta one off but well worth it when you’re out there on a western incline just lopin along when you used to struggle.
     
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