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Thread: How to turn up 3406B?

  1. #1

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    How to turn up 3406B?

    A friend of mine has a early ninety's peterbilt 379 with a 425hp Caterpillar 3406B, and he wants to turn it up a little. Is there any CAT experts in the house that can help? I think it's just a couple of adjustments on the pump and defeat the waste gate, and possibly bump the timting a little? I don't know, figured i'd ask someone who did. TIA

  2. #2

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    I would not recommed it, but many people have done it. There is a place here in Pittsburgh that could help, Diesel Injeciton. You would want to talk to Gary.
    01.5 ETH 4x4 ??????
    200,000+ miles

    We Are Penn State!!!

    "I Don't Need No Instructions To Know How To Rock!"
    -Carl from ATHF

  3. #3

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    Is the fuel injection pump on it fully mechanical or is it the PEEC pump? I know the barrel/plunger assemblies can be changed, without putting the pump on a test stand.

  4. #4

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    There are all sorts of little things that can be done to the 3406B to get a little more power. Big power increases will require pump work, as well as larger injectors and a turbo to match.

    Does the engine have an air to air, or an air to water intercooler? Re routing the AFC line closer to the turbo will bring low rpm fueling on faster, as the AFC will respond better.

    Does the truck have a fuel pressure gauge? Increasing the strength of the spring in the transfer pump located on the bottom of the injection pump will supply a steadier supply of fuel to the engine, so there will be less of a pressure drop under full load.

    Swaping injectors out of an offroad application, such as a wood chipper, marine motor, or gen set will show larger gains, but will also hurt economy, as well as increase EGT's, and water temps, if it is an air to water after cooler.

  5. #5

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    The way we did it the shop I worked at is to pull the timing advance off and make sure it isnt slipping. Then pull the injectors and have them tested, but dont change them unless there is a problem other wise it will take about 60000 miles for them to open up and start to run right. Test the afc and make sure the diaghram is good, we would just put a kit in it. Get the valves set and make sure they have no drag on the feller guage when its done, but you dont want they to click. Get the fuel settings set to high side stock. Now have the timing set to the top quarter of the timing graph and set the afc. Have the aftercooler tested for leaks, We would see alot of them broken and leaking. Test the fuel pressure with a manual guage should not drop below 20psi in a hard run, also make sure the aircleaners are good. Last you might think about putting a pr4 valve on butween the air compressor and the airdrier, We found that boost would go out the bottom of the airdrier when it was open. The pr4 has a spring in it set at 40psi so that it takes 40psi to open, the boost wont do it but the compressor can with no problem. This would make most of the drivers very happy, If you want alittle more you can try to get them to go 10% over but usually it wasnt needed. This should give you good power and economy. On the injectors if 2 or more are bad put in a set so the engine stays balanced, And like I said new injectors are not a bad thing it will just take a while for them to break in. Good luck and let us now.

    99 2500 3.54 gears auto just bought it on 12-27-03 with 100,800 as far as i can tell all stock. 2" front lift 285 BFG allterrain tires, no muffler. On 3-1-04 added a EZ,10-7-04 added d70 detroit locker

  6. #6

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    I work for Cat dealer pm me with the engine serial number . I can see what can be done. .

  7. #7

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    supersonic,i would listen to catmantom since he works for a cat dealer. dont call cat, nobody that works for cat or a truck dealer will turn it up,u need to be carfull,you r messing with a 2500 to 3000 to rebuild that pump by a dealer. if you get it out of wack it will run like a detroit(crap). ohhh by the way catipillars mechanical 3406 b does not have injectors, it has nozzles and a fuel pump,just to let u know.

  8. #8

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    Trust me on my above post, I spent 10 years as a cat certified mechanic at a kenworth dealership. To do it right follow what I said above and I dont think you will be dissapointed. If the engine has lots of miles on it the timing advance is probable slipping. The valves should be set every 100,000. Good luck, Mike.
    99 2500 3.54 gears auto just bought it on 12-27-03 with 100,800 as far as i can tell all stock. 2" front lift 285 BFG allterrain tires, no muffler. On 3-1-04 added a EZ,10-7-04 added d70 detroit locker

  9. #9

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    Fully manual, air to air, I'll get the ESN ASAP. Thanks a bunch!

  10. #10

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    I run the serail numbers thogh cat and found out the engine is as follows Sales Model: 3406

    Built Date: 16Mar1988 Tested Date: 26Mar1988 Shipped Date: 30Mar1988

    Tested: BB Plant: Mossville Test Number: 01 Cell Number: 02


    Test Element Test Value Spec Value Label

    Spec Number 0T7799 0T7799

    Arrangement Number 9Y2447 9Y2447

    Corr Fl Power 418 417 HP

    Speed 2,097 2,100 RPM

    COR FL FUEL RATE 20. 4 20. 4 GAL/HR

    CSFC 0. 346 0. 346 LB/HP-HR

    Adj Boost 33. 4 34. 6 IN HG

    Fuel Pressure 35 35 PSI

    Oil Pressure 69 64 PSI high ilde




    Torq Ck Speed 1,198 1,200 RPM

    TQ CK COR TQ 1,426 1,421 LB/FT

    Low Idle Speed 705 700 RPM

    Low Idle Oil Pressure 40 34 PSI

    High Idle Speed 2,333 2,330 RPM

    Response Time 5. 3 5. 4 SEC

    FL ST F SET 0. 118 0. 118 IN


    The 3406b has small connecting rod journal size and turning up any part of the engine the lower end will not hold much more an it was built for. Most important is how many miles and hours do you have on the engine ?What is the turbo boost at above is , The spec when the engine was built in 1988 is above and how is the blow by on the engine if there is alot ?

  11. #11

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    It has 213k miles, low hours, boost is 28lbs, minimal blow by (less than my 98 5. 9) He the owner/driver comlpains that it has low power on hills with 36k,gross load. i know they built these engines speced up to 600HP in some applications, he doesn't want to Tear real far into the engine, unless it needs it, (ie: rebuild) but is willing to do a turbo and or nozzles, but if the rods are really that weak (why so fragile?) then I guess well have to leave it alone.

  12. #12

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    If the boost is at 28 psi thats 5 psi below what it was when it left the assemble line,I would have the fuel system checked out low boost can be low fuel delivery too the cylinders, and timing. The connecting rod jornals are 3/8 of narrower then the later 3406C the early 3406C had narrow bearing the lower end was beefed up 3406C later serial numbers. That engine pushed 418 hp 1426 rpms he got to chug that engine.

  13. #13

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    If its fully mechanical, not a peec like bryan asked then pop the peanut cover off, back out both screws a 1/2 turn and then turn the AFC in one turn. Watch the pyro and boost. I would do this AFTER making it run to orignal specs from up above. After setting the valves, and checking the advance. Also the boys had a bull hauler on the dyno the other day that was "low" on power. It was a 425 3406 B dynoed at 450 at the rear tires. Found a governor spring weak, installed the correct new one and it was putting down 500 at the back tires. It too was an old B model. Another old black Marmon came in the other day puttin 525 at the back tires with a B model 3406. It had a differnt charger on it though.

    Another approach is to crimp the AFC line off and take the guts out of the AFC housing. This will make good response, but lots of smoke.

    I agree that new injectors will cause a power loss. They are notorious for "growing" with age.

    I did the above tweaks to a buddy's cab over pete 84 model. It has passed many new trucks hauling around a large tile machine on interstate 80 here in Iowa! Had a couple of guys try and run with him the other day and they couldn't. Not too bad for an old 400 horse 3406 JWAC with close to a million miles on it.

    Last edited by MMiller; 03-27-2005 at 08:35 PM.
    1993, 250, 4x4, 5sp, 3.54, HX40,4" exhaust, "adjusted" pump, Bosch 185s,
    1985 Crew Cab D350, Cummins, auto-eventually to be a built 47rh to go with the dana 80.

  14. #14

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    The connecting rod jornals are 3/8 of narrower then the later 3406C the early 3406C had narrow bearing the lower end was beefed up 3406C later serial numbers. That engine pushed 418 hp 1426 rpms he got to chug that engine.

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