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Thread: Building a GM EFI Small Cap Distributor for TBI Conversions!

  1. #1
    EFI GearHead ! EagleMark's Avatar
    Join Date
    Feb 2011
    North Idaho

    Building a GM EFI Small Cap Distributor for TBI Conversions!

    Fuel injecting other make motors takes care of the antique fuel delivery system. But you’re still left with points, or an electronic ignition that has no capibilities of the ECM controlling spark. So it would seem to take advantage of the full capabilities of the EFI (electronic fuel injection) there needs to be a connection between the two.

    The GM small cap HEI distributor used in many fuel-injected cars from mid 80’s to the mid 90’s was a perfect match. Plug in wiring, over the counter parts, plenty of donor vehicles and a proven record of reliability. Having this ignition system would give the ECM control of not only fuel but ignition timing as well!

    Putting the two together is a little more than most do it yourselfers can handle without some good machinist skills. The process and assembly with picture and specifications is outlined here for those qualified. For those unfortunate enough to not have a lathe there is information below of the machinist who helped develop this distributor to get yours done.

    Here’s a picture of the two distributors needed.

    For this write up I am using an International Harvester Distributor. But you can do this hybrid swap with any distributor, I have done them for Ford, Jeep, Mopars and IH. Bottom one is the Holley brand IH distributor (note: I’ve never found one that says Holley on it)
    Top distributor is a GM small cap distributor.

    Remove all points or gold box electronics and advance weights from the IH distributor or other brand. There is a clip under the oil felt in the center of the shaft that must be removed. Before removing the gear place witness marks on shaft and gear for re-assembly. This gear needs to be pressed off and on and the gears are unique to each distributor do to machining. Plenty of WD-40 in the shaft and twisting will get the oil build up off the middle of the shaft, then it will slip out. Inspect this shaft for unusaual wear or damage. I have yet to see a bad one.

    Then Diassemble the IH distributor down to the shaft and remove the pin holding on the advance mechanisim so you have just the shaft.

    Dissasembling the GM distributor is a matter of removing the pin holding on the gear and most gears pull off. Be careful of the reluctor on top of the shaft, it is pressed on and can be easily damaged. Plenty of WD-40 in the shaft and twisting will get the oil build up off the middle of the shaft, then it will slip out.

    What’s left is two housings and two shafts that need to be machined. They have to be thoroughly cleaned. A carburator parts dip tank works great.

    Here’s a look at how the distributors go back together.
    After machining and thoughroughly cleaning the parts insert the GM top shaft through the GM housing and install the IH bottom shaft. Line up the roll pin holes and install the roll pin. At this point the bottom IH shaft is inserted into the lathe and the two sections are trued.

    Slide the IH shaft into the IH housing and line up relief notches for the screws from the ignition module. These notches must be large enough so no binding occurs when tightening mounting screws.

    Install top mounting screws through machined holes in the top GM housing. They line up with the mounting holes in the original IH distributor.
    Here is the top view.

    Here you can see the mounting screws using the existing holes in the IH distributor.

    Line up witness marks on the IH shaft and gear and press into place. Install a new roll pin. Check for at least .035 free play clearence between the gear and housing on the IH. For other brans check the clearence before you take them apart.

    Now if your GM style fuel injection system is already installed just plug this in and your ready for a test drive.

    If you can't machine or don't have the time, ship the distributors to:
    Mail with check for $150 to:
    2244 W. Lundy Blvd.
    Post Falls, Idaho

    Ph# 877-777-5343

    Attention Marlo

    FYI I have built these distribuors for just about any car that had a carb to begin with.
    Attached Images Attached Images

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  2. #2
    Join Date
    May 2011
    Lakes Region, NH
    I received an email from the company that produces these:

    The correct phone number for Tru-Line is (208) 889-1369. I am Marlo Vatsvog the developer of the small-cap distributor for the IH fuel injection system. I moved to Post Falls Idaho but failed to update the phone number. Please correct my oversite. This is my 1st visit to your site and as a result the phone has been incorrect for several years.

    Thank you,

    Marlo Vatsvog
    Hopefully this helps folks converting IH engines.

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