Big cam 3 400

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Adisiwaya, Aug 17, 2022.

  1. Adisiwaya

    Adisiwaya Light Load Member

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    Well 2 and half years later finally got enough time and money to start the swap of the 1985 Kw engine. Giving her a new heart. Taking the old 3406b windowed engine and swapping the engine to the Big Cam 3 400 cpl 625 in a 80 k100c cabover.

    I need some drastic knowledge from others. I have a vin for a 85 kw stock 400 in it so I can get parts for it for idea.

    I know there's plenty of guys that have swapped it over and I'd love all the tips from everyone.

    Some questions are the wiring is so simple on these mechanicals is there much difference from a 3406b to a bc3 400?

    Will the motor mounts from the 1980 kw k100c swap over to the 85kw? What's the specs for the torque on them? Will it sit the same as the 3406b in there?

    Can anyone give me a run down on specs? How much oil psi should I have? Its 50-60 psi running ATM starting it running it for a bit. Snapchat-2075710675.jpg
     
    jldilley Thanks this.
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  3. 062

    062 Road Train Member

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    Adisiwaya Thanks this.
  4. baha

    baha Road Train Member

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    Be careful about jacking the cab over past the tipping over point a come a long hooked to the frame and to back of cab will make it safer to get cab clear of Rad. and motor coming straight up and out, If you have both motor mounts and the flat bar still on the ft. of 400HP motor it will be easy to get it to bolt in, wiring for the alt. and water temperature sensor should be a easy hook up?
     
    Last edited: Aug 17, 2022
    BoxCarKidd, jldilley and Adisiwaya Thank this.
  5. Dino soar

    Dino soar Road Train Member

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    Wiring is virtually the same but it may be done in a different way.

    For example your starter and alternator and that type of thing should be the same. When you wire for the fan clutch/ ac circuit/ temperature probe/ warning light, that one may be similar but a little different. Best bet is map out all of that wiring before you take it apart and you could probably reuse the temperature and warning senders, etc. Depending which system of fan that you have some of them require air to turn on and some require air to turn off and that makes a difference in the switches and how it is wired.

    The rest of the wiring is no big deal.

    Actually the most important thing is that you have the correct fan and fan mount for the truck that you are putting the big cam into. I do not know if on the older trucks the fan mounts were more Universal or not I don't know. I only can tell you that when you transplant engines you have to have the right fan mount that works with that exact truck model. I put my engine into a newer truck so I needed the n14 fan Mount that is for a fld120.

    As far as I know the motor mounts are in the same spot. I don't know anything about KW honestly but with Freightliner those mounts are all in the same spot whatever engine you have. My truck had a series 60 which is quite a bit shorter. And interestingly they had a front mount on it that actually had slots that you could slide it back and forth. I was surprised that the big Cam went in exactly perfectly, in fact it went in so perfectly I had the drive shaft strapped up and when I put the engine and transmission in the drive shaft fell right into place in the yoke.

    Everything set exactly perfectly correctly on the correct angle and everything else.

    I'm sure some of the guys on here have changed from the cat to the cummins and have done the exact job so they can probably be of more assistance to you.

    That engine that you have in my opinion the big cam 3 is the best of all of the big cams and you have probably the most desired CPL number of all.

    I have a big cam 3 and if for some reason I was going to get another engine that's exactly what I would be looking for.
     
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  6. wore out

    wore out Numbered Classic

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    When it comes to the gauges etc, use what is original to the truck. The sending units, sensors etc are just NPT. The truck manufacturer decided those not engine manufacturer. So put what is on the CAT on the Cummins. Put it all as close as possible in the same location as in on thermostat housing etc. other than adding length or shorten as needed wire it back up exactly like you took it apart. No big deal
     
    Oxbow, LameMule, Roger McG and 7 others Thank this.
  7. Adisiwaya

    Adisiwaya Light Load Member

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    It's going to be jacked up unbolted headed for scrap. Tree ####ed up top of it was going to restore it but I let it sit to long and well nature be ######
     
    baha Thanks this.
  8. Adisiwaya

    Adisiwaya Light Load Member

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    Thank you big time. That's actually really helpful. I was going to rebuild this but I know before I bought it two cylinders were replaced for sure and with the high oil psi I'm not really worried as I once was. I'm currently in Washington headed to Wisconsin so this weekend I'll be taking parts off the cat to pull the motor soon. I am curious though. Would the big cam 3 flywheel be basically the same? I have a new clutch on there cat idk if it'll fit for the Cummins and also I'm having to have someone go through the 13 speed in the kw cuz guy I had it rebuilt didn't time it right and only acts like a 9 speed. All new bearings and synchro so would love to run that vs a reman. I'm actually lot less stressed about this now so big thanks.

    Do you happen to know if it's worth while too pull tranny and motor at once put it together outside of the truck and slide in or is it better to do it in pieces?
     
  9. Dino soar

    Dino soar Road Train Member

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    I don't know. I'm sure @wore out will know. All I can tell you is that the big cam takes the pot type flywheel 14 and a half inch. It can be upgraded to the larger flywheel from the n14. The correct kit is the eaton Fuller easy pedal 14 and a half inch clutch. Don't forget to replace the cross shafts and bushings if they are bad, they probably are bad, and go over all of the linkages for your clutch and make sure all the swivel ends and everything else are tight and work properly.

    I have always done that in one piece but it's a little trickier because on a conventional you have to have the right angle to get it in. I never did a cab over and again @wore out will probably have the answer.

    I would put it all in together in one piece if it's possible.
     
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  10. wore out

    wore out Numbered Classic

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  11. OLDSKOOLERnWV

    OLDSKOOLERnWV Captain Redbeard

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    Just a little FYI…..

    And I own both so I can assure you, there are 2 different clutches that can fit the Cummins, all according to which flywheel you have.

    I changed my flywheel, I can set the pressure plate and clutches up on the input of the transmission, then bolt the clutch up after the engine & transmission are mated together.

    If the cab will tilt up properly, it’s definitely easier to pull the engine & transmission together.

    Each truck manufacturer uses a different engine mount, although they are in the same location best of my knowledge.

    A lot of the sensors you should be able to swap over, as long as the threads are the same…. Like for your coolant temp gauge…..
     
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