Cat 3406B engine information

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by 5J Excavation, Jan 31, 2021.

  1. 5J Excavation

    5J Excavation Bobtail Member

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    Jan 31, 2021
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    Hey gents, wondering if anyone on here can give me some info on these 2 serial numbers. Build dates, HP rating and possibly a good route for rebuild kits.
    Thanks in advance.

    4MG29469

    7FB977(7or2)8
     
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  3. Roger McG

    Roger McG Light Load Member

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    4mg29469 build date 06/13/1988 a/r# 9y-2308 310bhp @1800rpm
     
  4. Roger McG

    Roger McG Light Load Member

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    7fb97778 build date 08/10/1987 a/r #7w-8925 ataac engine3406b build for freightliner no hp rating iirc the early 3406b fb engines needed ataac to achieve 425 hp
    7fb97728 shows same build date as above a/r# 7c-7171 also ataac engine no hp rating shown built or shipped to paccar
     
  5. 5J Excavation

    5J Excavation Bobtail Member

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    Jan 31, 2021
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    Thank you guys!! What would need done to get to 425hp with these engines? They are just builders, so all new parts anyhow.
     
  6. Roger McG

    Roger McG Light Load Member

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    I believe just a hunch without digging to deep in to the internals on the 7fb I am almost positive that engine being air to air that vintage was set at 425
     
  7. Roger McG

    Roger McG Light Load Member

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    the 4mg set at 310hp will probably require hard parts. Pistons,injector nozzles,governer spring fuel and torque settings,timing settings and a turbo to get to 425hp. I could be missing something but you have a better start on making a healthy 425 with the 7fb core you have IMO
     
  8. 5J Excavation

    5J Excavation Bobtail Member

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    Jan 31, 2021
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    Excellent!! Sounds like I will focus on the 7FB....looks like both injection pumps are the same.

    anything to do different to pull more hp? Nothing crazy, just not sure what they’re capable of.
     
  9. wore out

    wore out Numbered Classic

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    The 310 is gonna need pistons, pump cam, timing advance, governor, nozzles and turbo to make it a 425.


    The 7FB and 4MG pumps look the same but the 7fb uses a different pump cam and timing advance. If it has the 21 degree cam that's plenty of timing I wouldn't advance it any more. The 400 actually had more fuel than the 425. I would make sure it has the 21 degree pump cam, (it will be scribed on the end of pump behind timing advance) put a set of OR-3425 nozzles in it which flow a little more fuel than the 3421 it came with and a borg Warner 177148 turbo and let it ride.
     
    black_dog106 Thanks this.
  10. 5J Excavation

    5J Excavation Bobtail Member

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    Jan 31, 2021
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    Thanks for the info wore out...sounds like the 7fb’s are better all around then?

    where is the best place for parts? Or just strictly stay with cat parts??
     
  11. wore out

    wore out Numbered Classic

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    Nothing wrong with a 4MG. But if you want horsepower you need to start with a higher horse engine to start with or its gonna be expensive
     
    Roger McG Thanks this.
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