4.2 block to 4.0 head swap and MPI or TBI decision. I NEED HELP!!!

Discussion in 'Injection Tech' started by Anthony1982, Nov 15, 2018.


  1. Anthony1982

    Anthony1982 Farmall Cub

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    I hope im in the right department. This is not a thread of how to do, but more so of what I should do, and depending on you guys help I might need help on "how" to do, and at that point i can probably to my research or you guys can help me here. So here we go...

    I have an 88 jeep wrangler that i converted to TBI. Full 4.2L motor and head. First time working on a jeep wrangler. Ran great. However the motor started knocking and the passenger side motor mount bolts to block casting broke. So motor is holding on one bolt there. So decided to buy another motor and come to find out the motor i bought is a 4.2L (3235444) block with a 4.0L (0630) head. Intake manifold or exhaust manifold was not on the new motor purchased. So its missing. Its just the 4.2 block and 4.0 head with power steering and alternator water pump with fan assembly on it. no wire harness.

    My dilemma is what would be the easiest most cost efficient way for me to put this new motor together.

    1) Stay with my TBI and swap everything over? If so how would i do that being that its a different head (4.0)?
    a. Use the 4.2 intake manifold on a 4.0 head
    b. or use a 4.0 intake manifold and get a TBI adapter plate to fit the TBI on a 4.0 head
    2) Swap the head from my existing 4.2 thats blown over and do the same setup
    3) Get the 4.0 MPI manifold and do a complete fuel injector setup from a later jeep model

    Keep in mind im looking for the cheapest way to get it back and running. Thanks so much forum
     
  2. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    If the 4.2 intake and exhaust will bolt on to the 4.0 head, then seems like the easiest fix.
     
  3. Anthony1982

    Anthony1982 Farmall Cub

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    Do you make any adapter plates that fits the TBI on a 4.0 head?
     
  4. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    Is this the throttle body mounting gasket?
    Isn't the manifold a MPFI set up with 1 injector/cyl?
    [​IMG]
     
  5. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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  6. Anthony1982

    Anthony1982 Farmall Cub

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    yes I did research, and I also found that the 4.0 head from a later model flows better because of the smoother curves into the head, Kind of like the Clifford intake manifold. Where the 4.2 or 4.0 older model intake manifold has 90 degree angles. . Only concern there is that if it has a one barrel port for the TBI will it affect anything?
     

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  7. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    Both of those are MPFI manifolds.
    The one on the left is a standard log style manifold and the one on the right is a tuned runner style.
    The right is a beteer design for more even flow to each cylinder.
    Will the avg daily driver really feel a difference between the two? Probably not.
    But if you had both setting in front of you, i would use the one on the right.
     
  8. Anthony1982

    Anthony1982 Farmall Cub

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    Yes you are correct. However the 4.2L manifold runners are similarly designed like the one on the left. I guess question now is, will the intake throttle body port be a problem for the TBI to sit on top being that its centered and there will be no length for both TBI injector to probably shoot straight threw?
     
  9. c5wagner

    c5wagner Farmall Cub

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    Here's what I did for a while when I had my jeep 4.2l. I ran a jeep 4.0l to motorcraft 2150 adapter kit from a guy named gronk on ebay and then used the Hamilton injection motorcraft 2150 to GM TBI adapter all on the 4.0l manifold and with a 4.0l cylinder head. The gronk kit came with injector plugs for the 4.0l manifold and a few vacuum plugs.[​IMG]
     
  10. Anthony1982

    Anthony1982 Farmall Cub

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    That is very interesting! How did it run? Im going to see if Bill can make me a plate that would consolidate the 2 adapters into 1.
     
  11. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    You just have to pick a manifold and send me the specs for the bolt pattern and opening.
    Or the part the bolts to the manifold.
     
  12. Anthony1982

    Anthony1982 Farmall Cub

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    How much would it be?
     
  13. c5wagner

    c5wagner Farmall Cub

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    The setup ran great but I moved to California for work and had trouble with smog referees and the 4.2l was getting up there in miles so I did a chevy tbi 350 engine swap that the referees gave less grief about. I did need a new tune on the prom chip as the 4.0l head runs different than a stock howell setup. The only reason I used 2 adapters was because I had the motorcraft on there first and did efi after. A big benefit to the 4.0l manifold is that you can orientate the adapter on any way you choose, I ended up rotating the throttle body so the front was facing driverside. Don't forget the stock injector ports on the 4.0l manifold need to be plugged, vacuum caps with set screws did the trick.
     

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