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Thread: Lm7 to L33 swap

  1. #1

    Default Lm7 to L33 swap

    So I blew up my Lm7 motor in my 03 GMC. I want to get a junkyard non flexfuel L33 5.3 I have been told everything will work with my existing wiring, injectors fuel rail coils intake. Is this swap possible? If the electrical doesn't work can I use all my existing electronics from the Lm7 motor? Any help would be great.

  2. #2
    Jr. Mechanic
    Join Date
    Apr 2013
    East Central Iowa


    Should be fairly simple. Might want to grab the PCM for the non flex engine because of tuning issues.

  3. #3


    thanks zippstripp. I called chevy today and they were nice enough to help me out and they claim that it should work the PCM should actively adapt. But, I have read somewhere that the 04 and up 5.3 fuel rails do not have a vacuum modulator or a return line back to the fuel tank, although the fuel rail working pressure is the same. I know the injectors are slightly larger on the L33 motors so I was hoping to use those. could I use my existing fuel rail with the new injectors? does anyone know about this? I have already ordered the motor. 55k no front accessories and a 3 year warranty. it only set me back $1400.

  4. #4
    Jr. Mechanic
    Join Date
    Apr 2013
    East Central Iowa


    Not sure actually. Would bepend on if they were physically larger or just a larger flow rate.

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