AMC Distributor set up

Discussion in 'Injection Tech' started by Bill USN-1, Dec 9, 2012.


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  1. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    OK so what does AMC have to do with IH......
    Well as some of you know when that great labor organization known as a "Union" went on strike at the IH engine plant, it left IH short on engines for it's production. So they went and "out sourced" another make of engine to fill in until production was back up.
    Since IH already had a relaionship with AMC by using the 232/258 it was natural for them to use an AMC engine.
    The one they chose was the 401.
    Which is why the AMC/Jeep/AMX/Javelinguys all look for the IH with the AMC engine.

    AMC used a lot of other manufacturers parts on their engines. One of them was the Ford duraspark distributor.
    HMMM, where have I heard that before?

    This makes for a very nice and easy transition to a poor mans HEI and even better....EFI.

    For HEI all you need is the distr and the 4 pin GM ignition module and the GM TBI or Ford TFI epoxy core coil.
    Then just follow the ignition FAQ for the wiring.

    But for EFI there is a little more that needs to be done.

    In this write up I'll walk you thru everything including disassembling the disr. It's not really needed to perform the conversion but I like to clean and inspect everything while I'm doing the conversion.

    First here's the distr i will be using. Look for an 80's model V8.

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    Let me start off by saying that a lot of people don't really understand what i mean by "phasing". It is the relation of the rotor to the cap terminal and the reluctor wheel to the pickup coil.
    Both of these together set the proper relationship for the spark to jump to the cap terminal at the correct time.

    What is a little confusing is that nothing physically moves in the distr except the shaft spins with the rotor on it.
    The spark jumps from the rotor tip to the cap terminal.
    The important part is as the timing increases more BTDC- before top dead center, it makes the spark jump from the tip of the rotor sooner and sooner. Si if you drill a hole in the top of a distr cap like I will show here, and then start the engine and shine the timing light on the rotor in the hole, it will look like the rotor is moving as you increase the rpm/timing.

    The important part to remember is that on a V8 cap there is only 45* between the cap terminals.
    If your timing increases so that the rotor is more than 1/2 of that then the spark will jump to the cap terminal ahead of it because it will now be closer.
    This is why phasing is important. If you left the phasing stock you run the risk of "arc over' when the spark will jump to the cap terminal ahead of it. At 2 or 3 or 4000 rpm this can can really cause a bad misfire.
    I get emails and PM's and phone calls all the time from jeep and AMC guys that tell me their engine starts and runs great, but when driving there is a really bad misfire....it is normally the phasing was never set for EFI. Some guys get away with it because they never optimize their timing curve for their engine. Or they just retard the timing until the problem goes away. neither is a good thing for power or MPG.



    This is where the phasing is on a standard carb distributor. The reluctor will be lined up.

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    And the rotor will be centered on the cap terminal. That's because the center shaft moves with the rpm and the base plate moves with the vacuum adv. These mechanically move the advance BTDC.

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    But to be properly phased for electronic timing control the rotor need to start further retarded (ATDC) so that as the timing is advanced the rotor will sweep across the cap terminal.

    More like this.

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    And if we remove the cap we will see just how far off the reluctor now is when the rotor is in the correct position for EFI.

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    So what do we need to do to correct this?

    Well first we need to remove some parts.

    The reluctor is simply keyed on the shaft with a small roll pin.
    Us a couple large screwdrivers and insert under the very center of the reluctor on opposite sides and pry it straight up and off.


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    Then you can remove the 2 screws on the base plate and the 2 holding the vacuum advance on and you can remove everything off the top.

    You can see I also removed the small circlip holding the pickup on the base plate.


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    Now you can see the mechanical adv weights that move the center advance shaft.

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    To make it easier to see I will remove the entire shaft from the distr.
    If you want to do this you need to remove the roll/spring pin that holds the lower gear on.
    I don't know why AMC only drilled this 1/2 way thru but it makes it a PITA. I used my 6/32 tap and carefully tapped a couple threads in the pin. Then I used a screw and a pair of wire cutters(dikes) to extract the pin.

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    Now that the gear is off...oh take note that the gear has a dimple in it. That lines up with the rotor when installed.

    We can now work on the mech adv. There are many ways to do this as is shown in the other distr FAQs. For this one, since I already had the 6/32 tap out, I decided to just drill a hole thru both plates and install a screw.

    Here you can see the hole i drilled and tapped.

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    And the screw I installed. I tapped thru both holes so the screw would lock in on the top hole. I did not want to pull the 2 plates together, I just want to lock them in place.
    A drop of locktite will help keep it there.

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    Make sure you remove any excess threads from the bottom so they dont hit the housing.

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    That's it.
    Now we put it back together.

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    And since i had my drill and 6/32 tap out. I also drilled and tapped the reluctor so I could use a set screw to lock it in place. (An alternative method to correctly set the phasing is to install the reluctor back in the stock location with the roll pin and rotate the advance plate clockwise until the rotor and reluctor phasing are correct and then drill and tap the adv plate to lock it into position.The vacuum adv arm will not be connected to the adv plate.)

    With the tapped reluctor.
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    (Alt method) Advance plate rotated on the AMC 6cyl distr
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    So to set the phasing I like to use an old distr cap with a hole drilled in it between the #1 cap terminal and the coil post. A step drill works good for this.

    You need to make sure you know what direction the rotor turns!!

    Fortunately for you....Here it is.
    It's CW.

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    Then we set the rotor so it's trailing edge is at the trailing edge of the cap terminal.
    That means the rotor has rotated past the #1 cap terminal and is heading for #8.


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    Then we lift the cap off and lock the reluctor down with it lined up on the pickup coil.
    Double and triple check this to make sure it is correct.
    You can see by looking at the pics how the original roll pin slot is now offset from the shaft.

    [​IMG]

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    That's it....
    your done. Now just wire it like in the FAQ's for EFI.
    Purple to P and org to N. Blk can go to one of the mounting screws on the ignition module.


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    Questions...comments...you know how to find me.
     
    Last edited: Apr 3, 2013
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