LS engine; To use stock wiring & ecm or after market

Discussion in 'High Tech Retrofits' started by alan0043, Jul 13, 2014.

  1. alan0043

    alan0043 Member

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    Hi Guys,

    I have a '71 SS Camaro. It has been sitting in the barn for over 30 years. It is time to get this car out. I would like to repower the car with an iron block LS engine. Maybe a 5.3 or 6.0 liter engine. I am in the planning phase. I have questions about the LS engine wiring harness and ecm. Is it better to get the wiring harness & ecm with the engine as a pull out or is it better to buy the harness and ecm after market ? What is the best cost effective way of doing this ? Stock ? or after market ? This question is for the guys who have repowered their cars before. If you had to re-do it over again which way would you do it ? Is there anything that I am missing ? I have never done a project like this before. So all help is welcomed. :)

    All opinions are welcomed. Thanks for any help.
    Al
     
  2. Randy S

    Randy S Veteran Member

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    I re-worked the stock harness on mine. That allowed me to place the relays on a panel near the battery and lengthen the harness so I can mount the PCM under the console. It's easier to order what you want, but I wanted the experience and would do it again. Spend some time searching the site - lots of discussion on harnesses.
     
  3. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    IMHO it is always better to use OEM stuff because it's higher grade, and will be modifiable in the future with tunes.

    Alot of the aftermarket junk peddled is locked.

    I've done 2 LS swaps this way. My last one was done by the McCullough brothers @ www.lsxharness.com
     
    Last edited: Jul 13, 2014
  4. LT1 WS6

    LT1 WS6 Veteran Member

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    Get the factory ECM, harness, and, if necessary, the gas pedal and throttle control module. You can always sell these items afterwards, but having them in the beginning is better I think. If you get the manuals and study the wiring, you can rework a factory harness yourself. It looks daunting but it really is just time consuming. There's a lot of help out there for you.
     
  5. Leonards78LT

    Leonards78LT Veteran Member Lifetime Gold Member

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    I custom built my own harness and reprogrammed my own computer for my Camaro. It was easy for me, because I have been in the fuel injection game for years, plus my years of experience in the electro-mechanical field for years.

    I agree with LT1 WS6, get everything!
    Manuals with the schematics are a must.

    Depending on your skill level will determine if this is a project or a nightmare.
     
  6. orkin

    orkin Veteran Member

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    If you plan on using the drive by wire intake, you might not have many options other than the factory ECM.
     
  7. SupplySgt

    SupplySgt Veteran Member Lifetime Gold Member

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    We used the factory wiring and PCM with the L31 in my 78. I didn't own the car at the time of the swap but I helped with it. They retained the TH350 but left the 4L80E wiring intact which is helpful now that I'm about to install that tranny.
     
  8. TheMeat

    TheMeat Veteran Member

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    I bought a new harness that is custom made to my application. All new wiring, connectors, wrapped in black mesh and none of the plastic split loom sh*t.

    Originally I planned, paid for, and sent my stock harness to get re-worked. Got scammed out of my money and harness so I went to a local shop that does harnesses and had them make this one. Hindsight....
     
  9. 73 L92

    73 L92 Veteran Member

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    I've done a half a dozen LS swaps. Used the factory GM computer and harnesses from either Howell or Speartech. Neither are cheap but all have worked flawlessly. Both have good tech support.
    Both needed tuning after install for the best performance.
     
  10. Steve T

    Steve T New Member

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    I'm doing an ls swap myself. After weighing out costs I'm actually going carbureted instead of EFI.
    I'm well aware of how much more efficient EFI is but the simplicity of working with a carb is more benificial for me. I'm very " old school" and the idea of learning how to use ls suite or a facsimile there of is more than I'm willing to deal with.
    Also, EFI upgrades can drain even a healthy budget pretty quickly. Have you seen what a FAST intake goes for?
    Nothing against FAST, they are the best of the best IMO. But again, I'm looking at the budget.
    Just a thought.
     

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