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1990 c1500 6.0 swap


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  • 1990 c1500 6.0 swap

    Hey fellas, Ive got a lot of questions here so bear with me. Im sure this has been covered in one form or another but I cant find exactly what Im looking for. My truck is a 1990 C1500 4.3 tbi v6 with a 5 speed. I have got my hands on a 2002 complete dropout LQ4 6.0 and 4L80e trans. SOOO... im trying to figure out how to go about this whole thing. A BIG part is figuring out engine mounts to go from the dinky little 4.3 to the Gen 3 V8. THEN, taking all mileage and personal preference out of it, will it be an EASIER and CHEAPER swap to stay fuel injected or go carb? its registered antique so worrying about emissions goes out the window.

    I know with the carb I can re use my throttle cables and cruise control cables. Also, the little MSD box makes wiring the engine to start and run very simple. Also Im assuming if I use my original oil and temp sending units, my gauges will still work too. Also can I use my stock fuel system with a pressure regulator to feed the carburetor? How would the 4L80e be controlled? How would the speedo work?

    if I put all the fuel injection components back on. I know I will need to change up the fuel side of things first off. I will also need the ecm tuned. How would my cruise control work? I dont really have a clue as to how I would wire this up so that everything continues to work properly like air conditioning and the like. Im guessing the factory computer from the gen 3 engine would run the transmission but still unsure of the speedo?

  • #2
    Re: 1990 c1500 6.0 swap

    I feel like a lot of your options are going to be personal preference. But you are asking the right questions

    Depending on how much of the donor setup you actually have (even though you said complete, sometimes there are different levels of complete) it might be cheaper to maintain the fuel injection, but you will have to provide fuel and have the PCM reprogrammed to bypass the anti theft feature (it's commonly called VATS) IF you can find the wiring diagrams and make sure to get everything wired up. Or you can buy a standalone harness or make one from what you have... There is also a converter that can run your cable driven speedometer from a speed sensor, but it's like $300 by itself. Or you may be able to use the cluster from a 91 or later vehicle that had the 4l80e tranny because it is electronically controlled (I have one I could send you for the cost of postage) but you would still have to do some work to get the readings accurate for your vehicle. 2002 should also be throttle by cable as well, you would just need a different cable.

    Running a carb obviously would require the intake, the ignition control and transmission control. I'm not sure how much all of those parts would end up costing.

    Either way the V6 and gen1 V8 use the same mounts, so you would just need the mounts for any LS swap. A/C is going to be different than what you have because there is no idle kick up currently on your truck due to the fuel injection. The FI system already has it in place for the LS system. The gauges should work with the existing sending units just on the new block. The temperature sending unit may need you to run 2, one for the computer and one for the gauge. That was a factory setup on the 90 though.


    • #3
      Re: 1990 c1500 6.0 swap

      One question that you asked that I don't see addressed above is the fuel system question. The 6.0 runs a 60# fueling requirement whereas I believe that your current setup requires only about 5 or so. The answer to that question is it needs to be upgraded. The pump will not supply enough pressure and the fittings on the lines were not designed to hold up to the pressure needed now. Also, your donor motor is likely to be a returnless style fuel rail. That needs to be addressed as well.


      • #4
        Re: 1990 c1500 6.0 swap

        There are motor mount options available as well. Some, such as those offered by dirty dingo retain all factory truck accessories in stock locations to include A/C.


        • #5
          Re: 1990 c1500 6.0 swap

          Got to
          All the info you will need is there.
          88 Ext. cab longbed TPI 350
          99 Suburban LS Vortec 350
          90 SWB Silverado 5.3l and 4l60e 4 sale will part out
          2003 Z66 Avalanche


          • #6
            So with a 90 model truck here is what you need to do.

            First, don't cut any wire until the truck is running and operational.

            You will need to do a stand alone harness, has the pin outs and diagrams of what to remove or cut out of the LS harness to make it work. You will need somebody to remove PATS from PCM, so find you a local tuner guy to help you with all that.

            Your cruise will work as normal as long as you leave everything in place.

            Personally I would go fuel injected. By the time you buy the Intake, MSD control box and carb you will be looking at over $1000

            Install a walbro 255 fuel pump or a fuel pump from a 96 and up Vortec truck. has to have 55 PSI

            Motor mounts are same thing as a V8 engine so no worries there.

            1990 SCSB Silverado