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1991 GMC C3500 Engine swap nightmare Help

Discussion in 'Engine Performance + Maintenance' started by surplusdoctor, Jun 23, 2012.

  1. surplusdoctor

    surplusdoctor Newbie

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    I have a 1991 GMC Cab and chassis c3500 that had a tired 350 and a good 4L80E in it. I pulled out the 350 and set in a new 454 tourque converter and bolted up a machine shop remanufactured 454 from a 1994 c3500.

    After I set it in I noticed the 350 TBI wiring harness will not support the eletronic EGR on the 1994 TBI intake. I have the 1994 computer I could use, but I dont believe it will work with without the electronic EGR.

    I bought a 454 1994 fuel pump for the fuel tank in the truck as I only have the 1994 TBI.
    I also bought the wiring harness adapter to connect the 454 TBI to the wiring 350 harness. I was told I should change manifolds and go to the style EGR that is on the 350 and have a chip made for one of the computers I have.

    can I get some advise as how to assemble this mess and truely make it work correctly?
     
    Last edited: Jun 23, 2012
  2. surplusdoctor

    surplusdoctor Newbie

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    I am doing the exact same engine swap. I replaced the tork converter with a 454 type into my 1991 GMC C3500, I am using the original wiring harness and the 350 & computer with a towmaster chip for the 454 installed. The 1991 wiring will not support the 454 TBI 1994 computer or electronic EGR or wiring harness. I had to buy an intake manifold for a 91, 92, 93 7.4L that uses the Vacuum EGR . I used the 1994 TBI and yes you have to change the fuel pump in the fuel tank.

    I went with a HD oil cooler in front of the radiator. The 4 core radiator on the Cab and Cassis has a oil cooler in the drivers side tank, But I elected to not use it. I have an all most new set of lines if you need them, I never started the engine, but I snapped them on to the engine, then decided to go the external cooler. Bought the HD external cooler lines from a dealer because I couldnt find after market for the HD external cooler.

    Now I am to the point where I am trying to figure out the map sensor, and other items that were on the 1994 454 and the 1991 350.
     
  3. Horns

    Horns Tiff's Wedding Crasher

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    Do you have a complete donor truck? I might have been easier to use the 454 harness and ECM.
     
  4. bluex

    bluex Mall Crawlin' MOFO!!!

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    I don't think he realizes he's talking to himself :shrug: :rofl:
     
  5. Horns

    Horns Tiff's Wedding Crasher

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    I was wondering that for a good 5 minutes, then I kind of thought maybe he was just saying "Hey guys, I'm still working on the same thing except now..." kind of thing.
     
  6. 1low95GMC

    1low95GMC I'm Awesome

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    Fail lol :)
     
  7. bluex

    bluex Mall Crawlin' MOFO!!!

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    I was thinking that to, until I got to the part where he offered to sell himself his oil cooler lines.


    OP, I would just set the thing up like its a 91 model 454 an not worry with the stuff from 94. Just my .02 though
     
  8. Horns

    Horns Tiff's Wedding Crasher

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    I was reading the confusing paragraph so fast that I skipped over that. :rofl: We need a "Best Off" section and this needs to be in it.
     
  9. LT1/TA

    LT1/TA Newbie

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    Awesome:hmm:
     
  10. bluex

    bluex Mall Crawlin' MOFO!!!

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    Ya a best “off" section would be great! :rofl:
     

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