4.3 to 5.7 swap, a couple of questions

Discussion in '96+ Vortec Performance + Computer Swaps' started by jimdaug, Apr 12, 2018.

  1. jimdaug

    jimdaug Newbie

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    I've searched a around a bit but haven't dug into my service manuals yet, just hoping for a couple of quick "should or shouldn't work" type answers. I'll work out the details later.

    I have a 97 short bed with a 4.3. I might be able to get a 5.7 motor, trans and harness w/pcm from a 98 for a decent price.

    Would it make more sense to try to use the 98 harness, or just change what I need on the 97 4.3 harness to make it work with the 98 pcm and 5.7?

    Or would it make more sense to try and find a 97 5.7 harness and computer?

    Motor mounts: Are new motor mounts complete, or is there a separate piece on the front cross member that I have to find?

    And thinking forward for a supercharger are there larger cc combustion chamber 5.7 vortec heads that I could bolt on while I'm at it or is the smaller cc chamber a defining element of the vortec heads?
     
  2. df2x4

    df2x4 Domestics only.

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    I know the PCMs and wiring changed in '98, there's an extra harness plug that the '97s didn't have. Passlock was also introduced in '98 so you'd have to fight that. I'm sure it's doable, personally I'd look for some stuff out of a '96-'97 just to make life easier. I'm sure someone here can tell you how to make it work, though.
     
  3. jimdaug

    jimdaug Newbie

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    Ah, yeah, good point on the passlock. The 98 harness would come with it either way so if I have to find a 97 PCM and harness it's still a good deal. And I have a feeling I'll end up stealing wires and connectors and what not from the both all three harnesses as the case may be.
     
  4. L31MaxExpress

    L31MaxExpress I'm Awesome

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    On my 1997 5.7 Express van the 5th plug went to nothing. It looped back to itself about 12" down the harness. Just an observation I found doing my 0411 swap.
     
  5. chevyjack

    chevyjack Newbie

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    I know this is old but, i have 98 4.3 5 speed. Found a complete high mileage 96 donor truck 350 5 speed. kind of the same question as previously asked, would it just be easiest to take everything off the 96? Harness and computer?
     

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