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  • Switching from YJ 89 carb 4.2 to YJ92 FI 4.0

    Hi Folks,
    I have a 1989 wrangler, 6cyl, 258, 4.2, auto, np231, 4x4, nutter by-pass, carter BBD. It is street driven weekly and also used for plowing snow in winter and fun in summer. No lift kit installed or serious off-roading, and has approx. 25,000 miles since last complete overhaul. Power is OK.

    I have the opportunity to install either a six-month old Weber 32/36 DGEV carb, or a 1992 6cyl, 4.0 fuel injection system. The 1992 has engine, auto tranny and np231 xcase still mated together as one unit and comes complete with wiring harness, ECU and sensors. I am assured this system was running and functioning six months ago before the vehicle was side lined with full frame and body rust failure in all the usually places, at 112,000miles. The price is right on either choice.

    I have tools, mechanical ability and a super resource in 4WD forum experts.

    Now for my questions:
    Which route would you go?
    Why?
    Will the auto tranny on 4.0 exactly interchange and mount to the 4.2 block?
    The Weber switch is obviously the easiest conversion, but is it the best?
    Will the head on the 4.0 bolt up to the 4.2 block?
    Would the fuel pumps need to change?
    Would the intake and exhaust manifolds from the 4.0 bolt to the 4.2head?
    If I swapped the engine-tran-xcase as a unit, Would the motor and xcase mounts line up?
    What else should I be thinking about?

    Thanks for your help,
    Sincerely,
    Jimbob

  • #2
    Here's an interesting read about swapping in a 4.0 head and components to a 4.2 engine block. Might answer some of your questions. As for the other components, keep in mind the high mileage of the 92 parts, especially the auto tranny and t-case, unless they have less mileage than the parts in your 89 rig.

    http://jeep.off-road.com/jeep/articl....jsp?id=277013

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    • #3
      I do believe that all of your questions could be answered as, Yes.
      But the question you need to ask is how much work do you want to do.

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