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  • 4.3 TBI on 4.2?

    Looking for cheap fuel injection for my 4.2 I6. My understanding is Howell makes a kit that uses the chevy TBI from the 4.3 V6 and adapts it to the AMC 4.2.

    Here's my question. Has anyone done this swap on their own without the Howell kit? (i.e take TBI from junkyard 4.3 and swap it to a 4.2.)

    I have searched some on the internet but have not found anyone that has tried this. If Howell can do it, I am sure we can figure it out.

  • #2
    The hard parts don't care what kind of vehical they are on,it in getting a correct program for the engine it is going to run on.There are several systems that are avalable for the computer system

    TRY AGAIN
    Last edited by jeep450; 07-20-2005, 05:34 PM.

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    • #3
      I couldn't get the link to work. Couldn't the computer come from the donor vehicle along with any sensors needed? I have a non computerized HEI with mechanical advance. Could that be made to work with TBI?

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      • #4
        Your HEI can work with the TBI. What Jeep450 is talking about is the Prom chip. Inside of the ECM there is a chip which contains all the needed info for how the engine needs to run. It collects the data form the sensors and adjusts the fuel input accordingly. Not to say that it can't be done but sometime's it's a time vs money thing. If you have a the time to source the parts, pull them at a yard (cause if you don't they'll hack it), and figure out the wiring then go for it. You will also have to get the Prom reprogramed or a new one burned. I think you can get it don for around $20-$30. Only thing is if it's not right you have to do it again. My suggestion if you are going to go through that I would go pull a MPI system from a 4.0 and go that route. Granted it might cost a little more but will be well worth it.
        FWIW I 'm told that the MC 2100 carb swap works really well with the HEI. Runs good at pretty much any angle and power to spare. Just a thought if you are looking for something better on the trail for cheap.
        Last edited by xtrm4xjp; 07-20-2005, 04:10 PM.

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        • #5
          3.9L diesel eh? Now you're talking. I thought the 4.2 had torque but not diesel torque. I do not want to lose the torque the 4.2 has at idle compared to the 4.0.

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          • #6
            Fixed The Link

            The reason that the tbi computer will not work correctly is that it is calibrated for what ever it came off of and it will be trying to control the ignition timing and the fuel curve for what it came off of.The sensors will work,but if it thinks it is a 4.3 chevy, it will not run correctly for the 4.2 jeep.That is when a computer programmer will program the correct program in the "chip" for the 4.2.....found only by r&d to come up with the program.Also at that time they will take out the program for timing control,theft system ect.Does that make sense?It would be no different than taking a fuel injection system off a Ford and putting it on a Chevy, it wouldn't know what the heck is going on b/c it thinks it is still on a Ford.

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            • #7
              I think this is the address that will explain most everything you need to know about swapping the EFI.

              www.customefis.com

              The above comments are mostly correct, with a few exceptions. Ford EFI on a chevy motor (why would you want to) should work just fine if you use the Ford Mass air flow system. MAF systems measure the total volume of the air entering the motor and adjusts the fuel charge to match! Sooooo, the FI from a ford 300 six would work jsut fine on a 258, provided you could mout the hardware on the motor.

              The main problem with the GM retrofit is the spark control. GM uses a table stored in the PROM chip to calculate total advance based on RPM and MAP (Manifold Aboslute Pressure an indication of engine load). The 4.3 spark table and the 4.2 spark table may be different. Howell addreses the problem by eliminating the spark control and using the stock dizzy to spark the engine. The guy at customefis reprograms the spark table and then uses the stock pickup assembly to fire a GM computer controled module.

              The fuel is also controled by a table, but fuel requirements for simmilar sized engines will be fairly simmilar. Odds are if you got the spark table to work (by using the 4.3 table and then adjusting the advance on the dizzy till it runs right), then the fuel table would be close enough to make it work. The GM computer will use the O2 sensor data to adjust the fuel table once the motor is up to temp.

              sorry bout the long post

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              • #8
                programming

                All I am trying to say is that it is all in the programming period.Any injection system would work on anything.Would it opperate properly or would you get maximum efficency and throttle response and keep the check engine light off beacuse it is having to lean out or richen up the fuel curve beyond what it is programmed to do .......no.That is ,for example Howell has done.They have MATCHED the programming, injector size and volumn for the conversion kits they sell.They have done all the research and devolpment to come up with what it needs to be.I'm sure that they don't just take a computer for what ever and just put their sticker on it.Could anybody take any fuel injection and make it work for themselves, sure if they could calcuate what size injectors to use, how to write the computer program for the right fuel curves and ratios and not to mention to have to equipment and the time to figure it all out.

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                • #9
                  Originally posted by junebug
                  3.9L diesel eh? Now you're talking. I thought the 4.2 had torque but not diesel torque. I do not want to lose the torque the 4.2 has at idle compared to the 4.0.
                  Yeah I really like the torque that little deisel puts out, kind of nice to be able to idle or just above through most things.

                  As for the low end torque, you will still have it even if you swap to a MPI system off a 4.0. Your torque is more to do with the bore, stroke, and cam in the engine then the delivery method of fuel. alot of guys are putting 4.0 heads on 4.2 blocks to get the stroke of the 4.2 (for low end torque) and the good flow of the 4.0 head. Some guys are also installing 4.2 crank and rods into a 4.0 block which creates a stroker motor. Just though I would throw these out there incase you didn't know.

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                  • #10
                    I frequently talk to a guy on a forum that has done this and it works amazing! Go here:. You'll have to sign up for a screen name and what not first, but once you do hit the link again and read on. He;ll be able to point you in the right direction.

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                    • #11
                      Thanks...there is a lot of information there!

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                      • #12
                        Yeah, its alot to take in. I'm hoping to do it in the next 6 months or so. If you go this route let me know how yours turns out.

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