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  • GM Throttle Body FI for 258

    I noticed in the current 4WD Hardware catalog a GM throttle body fuel injection adapter for the 258 six. This looks like an interesting route to get fuel injection. I'm really tired of carb problems! Has anyone made this conversion? What all is needed from the GM vehicle? GM throttle bodies should be readily available and reasonably priced from salvage yards.

  • #2
    Just buy the kit. The GM TBI retrofit to a Jeep engine requires reprograming the ECM Prom, and that takes a lot of Equipment (about $300 ) and time. The folks at howell have already done all that hard work and their Throttle body is new, not used, so it is a deal.

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    • #3
      I guess that would all depend on your ability to understand and build MFI.
      Here is an interesting Link , for a Fuel Injection Computer.

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      • #4
        I've looked at the Megasquirt and it would prolly be more work to put together than retrofiting a GM TBI.

        The details that I am talking about are creating a suitable spark table for an engine from scratch. You will need to know exactly how the spark advance curve changes based on engine RPM, load, A/F ratio, etc. In addition to the spark table, you will need to figure out the fuel requirements of the engine in order to determine the injector base pulse.

        Don't get me wrong, I think FI is great, and I don't want to discourage you, but it is a fairly involed process. If you do it right, then it will increase your power, economy and enjoyment, if done wrong, you will have a tempermantal pain, or worse yet, a non runner.

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        • #5
          You will need the GM TB and all it's sensors. You will probably want the wiring harness from the donor and the Computer for sure.

          The programming isn't too hard to do. I swapped a TPI 350 into my CJ and I ended up buying all the programming stuff. It wasn't too expensive.

          If anyone has the EPROM from a howell setup, I'm sure I could clone it. If not, it's not too bad to do one from scratch. You would want to start with a EPROM from a similar size engine so your initial program will be close. Then you just tune it from there.

          The thing I don't like about the kit, and the reason I bought the gear, is that the kit is setup for what it is. If you change anything, you really should reprogram your chip. Say you have a regular 258 and buy the Howell setup. It should run perfectly, but what happens if you put a header on or swap a 4.0 head? The program will need to be changed.

          Poke around this guy's site too... http://www.customefis.com/
          He sells parts and service for GM fuel injection swaps onto ANYTHING, but mainly Jeeps (including the AMC v8's). I've done a lot of research and it's not too hard. I will probably be putting a throttle body setup on my Grand Wagoneer's 360.

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          • #6
            Dperk nice link.
            Gotta add that to the bookmarks.

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            • #7
              I like my howell.

              Plus.. when (LOL.. this has been a long *when*) I go to a V8.. all I need is 2 more injectors & a new pooter chip & I am good to go with TBI on that (304 V


              -Mel

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              • #8
                here is some other good places to do research on GM EFI...

                http://www.diy-efi.org -> some info and a great mailing list
                http://www.thirdgen.org/techbb2 - Great for eprom burning info, TPI & TBI

                For programmers and stuff... www.moates.net

                That should be enough to get anyone started
                Last edited by dperk; 04-21-2005, 09:43 AM.

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