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  1. #1
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    Default 1991 GMC C3500 Engine swap nightmare Help

    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 by surplusdoctor; 06-23-2012 at 12:22 AM.

  2. #2
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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. #3
    Daily Dose Master Horns's Avatar
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    Do you have a complete donor truck? I might have been easier to use the 454 harness and ECM.
    -Jack
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    98 Silverado 1500 ECSB Dana 44 + 14 Bolt FF Isuzu 4BD1-T Engine 4L80E Transmission SOLD
    94 Silverado 1500 ECSB 3" Body Lift Cammed & Tuned TBI TBI and IFS Delete Kits Coming SOON!


  4. #4
    Mall Crawlin' MOFO!!! bluex's Avatar
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    I don't think he realizes he's talking to himself
    Paul #2 - My opinion is worth exactly what you just paid for it

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  5. #5
    Daily Dose Master Horns's Avatar
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    Quote Originally Posted by bluex View Post
    I don't think he realizes he's talking to himself
    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.
    -Jack
    >Iowa GMT400 Members< >DD Thread Schedule<





    98 Silverado 1500 ECSB Dana 44 + 14 Bolt FF Isuzu 4BD1-T Engine 4L80E Transmission SOLD
    94 Silverado 1500 ECSB 3" Body Lift Cammed & Tuned TBI TBI and IFS Delete Kits Coming SOON!


  6. #6
    I'm Awesome 1low95GMC's Avatar
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    Fail lol

    95 GMC Sierra RCSB 305, 5 speed, 5/7 drop, HI 4 mod, Quad sealed beam headlights, Custom bumper.
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  7. #7
    Mall Crawlin' MOFO!!! bluex's Avatar
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    Quote Originally Posted by Horns View Post
    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.
    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
    Paul #2 - My opinion is worth exactly what you just paid for it

    '98 Z71 ECSB - the daily - traded for an 89 gmc crew cab :doh:
    '78 GMC Sierra 15 - a forever project
    '02 burb - "da bus"

    RCX lift kit install tips

    http://gmt400.tumblr.com

  8. #8
    Daily Dose Master Horns's Avatar
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    Quote Originally Posted by bluex View Post
    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
    I was reading the confusing paragraph so fast that I skipped over that. We need a "Best Off" section and this needs to be in it.
    -Jack
    >Iowa GMT400 Members< >DD Thread Schedule<





    98 Silverado 1500 ECSB Dana 44 + 14 Bolt FF Isuzu 4BD1-T Engine 4L80E Transmission SOLD
    94 Silverado 1500 ECSB 3" Body Lift Cammed & Tuned TBI TBI and IFS Delete Kits Coming SOON!


  9. #9
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    Thumbs up

    Awesome
    94 GMC ECSB 5.7,auto,3.42 gears,285/75/16 BFG At's,Dual Exhaust with Glasspack

  10. #10
    Mall Crawlin' MOFO!!! bluex's Avatar
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    Quote Originally Posted by Horns View Post
    I was reading the confusing paragraph so fast that I skipped over that. We need a "Best Off" section and this needs to be in it.
    Ya a best “off" section would be great!
    Paul #2 - My opinion is worth exactly what you just paid for it

    '98 Z71 ECSB - the daily - traded for an 89 gmc crew cab :doh:
    '78 GMC Sierra 15 - a forever project
    '02 burb - "da bus"

    RCX lift kit install tips

    http://gmt400.tumblr.com

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