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HEI with Electronic Spark Control

Discussion in 'Early CJ5 and CJ6 Tech' started by jayhawkclint, Mar 1, 2009.

  1. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

    Oklahoma City, USA
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    So, it seems our supply of junkyard '75-'79 Buick 231 HEI units is starting to dry up, odd or even. At first I completely blew off the '81+ units, but now that I'm looking at diagrams, it appears that its just a module and the distributor, and you do away with vac advance. There must be some kind of knock sensor involved, but haven't looked that deep yet. Anyone ever hook one of these up that could provide general guidance on how a Dauntless would receive one? Looks like the pickup and lobe conversion would be the same, and a module would get mounted to the firewall, probably where the ballast resistor used to go, but what about sensors?
     
  2. Mar 1, 2009
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    I think it's just an electronic advance. The module and ECU receive a signal from the pickup that is maximally advanced, then the spark control places the required delay after the trigger, depending on how much advance is called for. The ECU receives several inputs, including a knock sensor. However, I believe that the ECU will also retard the spark depending on temperature, load, speed, etc.

    The HEI module for spark-control still goes in the distributor, and has a similar size and shape, but it receives an additional signal from the ECU that retards the spark.

    AFAIK the modules are interchangeable, but I expect you lose the mechanical and vacuum advance on the electronic distributor, and it may not be trivial to put them back.

    Sorry if this is too obvious or basic, but I think this is what's going on with these, and it's not clear to me how you'd make one work on either the OF or EF engines without an ECU.
     
  3. Mar 1, 2009
    Colorado_Baja

    Colorado_Baja JEEPS!!

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    Your jeep/automotive knowledge never ceases to amaze me, Tim.
     
  4. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Yes, electronic advance. The thing is, I looked at a couple of these units on Quadrajet cars today that looked like it didn't have an ECU, just an HEI and a module about the size of a Duraspark module on the later CJ. I only saw 4 wires going between the module and the distributor, and maybe a couple more that *seemed* to head off to the block, not an ECU. The unit is definitely an electronic advance, and at first glance it looks really simple. I took one apart today, and the base is the same, internally same cap, same rotor, same shaft except there are no mechanical weights. There appears to be an extra piece of ignition module stuck down in the base. Coil looks similar if not identical. I Googled earlier, but didn't come across any really good diagrams, maybe I'll have better luck later on tonight.
    Posted via Mobile Device
     
  5. Mar 1, 2009
    w3srl

    w3srl All-around swell dude Staff Member

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    Man that would be really slick, doing away with the mechanical & vacuum advances. I would expect that theses distributors would be similar to the Chrysler units from the late '60-early '70s. I remember the "gold" box from Mopar's "Direct Connection" really woke up my little homebrew 340-6 in the Duster!
     
  6. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Bingo:
    http://jeepgarage.free.fr/OWN/ignition%20system%204.0l.pdf

    It appears that it normally is connected to an ECM, however comma:
    Terminal "B" of the 4-wire connector is the by-pass circuit.
    At about 400 RPM, ECM applies 5 volts to this circuit to
    switch spark timing control from module to ECM. An open or
    grounded by-pass circuit will set a code 42 and the engine
    will operate at base timing, plus a slight amount of advance​
    built into the module.
     
  7. Mar 1, 2009
    w3srl

    w3srl All-around swell dude Staff Member

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    <golf clap> :D
     
  8. Mar 1, 2009
    zed

    zed Iowa- Gateway to Nebraska

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    745
    Hmm.... so the one you found was from an 88 cherokee? I might tear one down run the tests in the pdf. Also just to see if the physical form would require a lot of changes.

    I'v wondered about substituting the module in my OF 231 dist...
     
  9. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Nope, the units I was looking at were from '80 through '86 (ish) or so Buick V6.

    Rest of the distributor looks like it would be a "routine" even to odd fire mod. As Tim stated above, this module that actually advances the timing is self contained in the base of the distributor and must be the extra little electronic piece I noticed earlier today. The only thing the ECM seems to do is retard the baseline based on external conditions, i.e. engine overheating, low octane, etc.

    I see some internet numbers (I saw it on the 'net, must be true, right?) that claim the module can do 24deg of timing based on engine RPM. If true, 8 to 10deg initial plus 24deg electronic equals 32 to 34deg total, about where my Dauntless seems to want to run.
     
    Last edited: Mar 1, 2009
  10. Mar 1, 2009
    zed

    zed Iowa- Gateway to Nebraska

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    745
    Yeah, I had read your other HEI post about the advance. For some reason, I haven't had the flat spot you were talking about even though I removed that vacuum advance. We'll see when I drive it in the spring after all the salt and brine has washed off the Iowa roads.
     
  11. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    What springs are you running? The stock springs that were in my non-computer donor were equivalent to about the strongest springs in a re-curve kit; I'm thinking I had good total advance, but the mechanical just wasn't kicking in soon enough.

    I'm really curious about this non-EFI EST or ESC HEI. Might have to pick one up just to take a peek. I eyed one that looked like it had recently received a tune-up. For $20, might be worth checking out, if nothing more than for intellectual property. If it works, it could possibly increase our pool of potential donors by orders of magnitude.
     
    Last edited: Mar 1, 2009
  12. Mar 1, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Okay, confirmed, the "computer" that retards the baseline is nothing more than the little module (about the same size as a Duraspark ignition module) that mounts to the firewall and runs one wire to a knock sensor, a wire to ground, a wire to switched +12vdc, and a couple wires to/from the ECM located in the base of the HEI distributor. Looks like a really simple deal, just don't know where I'd mount a knock sensor on the Dauntless.

    For your reading pleasure:
    http://www.autozone.com/az/cds/en_us/0900823d/80/17/06/5c/0900823d8017065c/repairInfoPages.htm
     
  13. Mar 1, 2009
    zed

    zed Iowa- Gateway to Nebraska

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    745
    The springs were stock. It IS out of an actual oddfire 231 though. I rebuilt it but kept the springs.



     
  14. Mar 2, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Hmmmm... I sorta just found mine one day among some random JEEP parts that were included in a fire sale I picked up, so I don't know for sure what it came out of, but it's a non-computer non-Chevy even-fire 6cyl, so pretty much always figured it had to be a late '70s 231.

    I'm wondering if I can mount a knock sensor on my Offenhauser 360. Apparently Buick did it in '78 and '79 on the Turbo models.
     
  15. Mar 2, 2009
    AKCJ

    AKCJ Active Member

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    From what I've heard you could mount the knock sensor anywhere on the engine. I've heard of drilling and tapping the block on a chevy v6. If you had to, you could mount the knock sensor to a bracket and bolt the bracket on but that could lead to false readings if it wasn't sturdy enough.
     
  16. Mar 2, 2009
    sdcj6

    sdcj6 Sponsor

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    Knock sensors on Chevys are mounted in the block drain holes near the oil pan, into the water jacket. Pipe threads on the sensor I believe.
     
  17. Mar 3, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    Dawgonnit. Fiddling with an even fire 6cyl Buick HEI w/ESC tonight. The parts are all interchangeable except the index slot for the cap that is cut into the base; Delco put it in a different position on the ESC model than on the vac/mech model. I suppose it wouldn't make a bit of difference if we were swapping around even fire parts, but when you go to bolt the odd fire points in there, the rotor ends up on an even point when indexed to #1 TDC. I can make this work using a base from the vac era and guts from the ESC era, but that defeats the purpose of this whole project with an eye toward expanding our sources of donors. I'm going to keep fiddling with it. I either need to re-index the points (drill and tap a new hold-down), or I need to cut a new slot in the base for the cap.

    EDIT - Looks like I'm just going to rotate the pickup coil about 45deg, drill a hole in the base and sink a long screw in with a standoff to keep it firm. (basically the distance between an even and odd point on the pickup coil)
     
    Last edited: Mar 3, 2009
  18. Mar 4, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    I messed around with it a little more tonight. I got a spark! So far just a couple loud bangs, though. I think I must've been off 360 on the timing mark. Going to do a little fiddling and see if I can get it to start. If this works, I'll do a writeup.

    EDIT - It works!
     
    Last edited: Mar 5, 2009
  19. Mar 5, 2009
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ

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    I'm currently running it in "open" mode, no sensors. I'll post some pics of the mod for now, then do a more thorough writeup someday when I figure out the sensors, shake out the bugs, etc. For now though, I can confirm this runs every bit as good, even in open mode, as a vac/mechanical unit does. I've got some tweaking to do, but it's at least moving under it's own power again.

    Top is my modified 6cyl dist shaft for use with oddfire pickup in a pre-computer HEI. Bottom is HEI/ESC dist shaft for even fire 6cyl. Note there is no provision for mechanical weights; all the advance is done through an electronic control module:
    [​IMG]

    Here is the base of a pre-computer HEI:
    [​IMG]

    Here is the base of an HEI/ESC. Note the notch is in the wrong spot for use with an oddfire cap:
    [​IMG]

    Here is the inside of my pre-computer HEI. This was an even-fire unit that I modded to oddfire. Compare notch postions to that of the HEI/ESC picture below in relation to the capacitor:
    [​IMG]

    Here is the inside of an HEI/ESC before modding. I thought the little brown piece to the lower left was an additional piece of electronics, but it turns out it is just a connector that routes a ground wire from the base of the dist out through the harness to the computer module. This is done to make sure that the module and the dist do not have a difference of potential that would cause a false high/low ESC signal. In the end, to run in open mode you simply unplug the whole connector and 4wire harness from the dist:
    [​IMG]

    The pickup coil on the HEI/ESC takes a different plug than the pre-computer coil. My pickup points separated from their respective coils, however, so I just swapped the oddfire points onto the ESC coil. It would be just as easy to clip the spades and crimp on smaller plugs:
    [​IMG]

    Now comes the fun part. The HEI/ESC base is notched in the wrong location for use with an oddfire cap. If you put it on, the wires end up on the wrong side of the base so that they won't physically reach, plus the pickup coil won't index to #1 TDC correctly. I had to reindex both the cap and the pickup coil. Most JEEP projects I would rate on a beer scale, i.e. a D18 seal is a 3 beer job, axle swap is a 6pack, tranny swap is a 12pack, etc. This is a ZERO beer job. What I mean by that is you only have a degree or two of slop either way; get it right the first try! Basically what you do is set the cap on top of the base to figure out where the #1 post is going to sit. Make sure the hold downs and the wire harness are in agreement. Use a file to etch a line on the side of the base. Pull off the cap, line up your modified reluctor to an odd lobe that is closest to your etched line, then rotate the whole pickup until your rotor is aiming directly at where #1 is going to be. Drill a hole in the base and screw the pickup down permanently; it doesn't move. Then, set the cap back on and make sure you got it right. If rotor and post are lined up, use the file to etch out where your notch needs to go for the cap, then use a grinder or Dremel to rough it out, and a jewelers file to finish it and square it off. The job itself is a simple task, just getting everything lined up is the only PITA part. Everything else about the mod is a "routine" even to odd HEI mod. I recommend this writeup: http://www.cjoffroad.com/writeup.asp?WU_ID=21&noAdd=1

    New notch is facing camera. An HEI rotor can only mount in one direction, and so in this case the rotor points off to the left and toward the camera. This is also indexed to #1 TDC in the picture. To the right of the pickup coil in the picture you can see my 1/2" standoff. Just drill and tap, dab a spot of expoxy onto the bottom of the standoff, then screw it down:
    [​IMG]

    Top view, you'll see the modified reluctor is indexed to an odd lobe, and the rotor (when mounted) points to where the #1 post sits. Unlike even fire systems, it is crucial that #1 actually points to the post that is #1; you can't just randomly pick a post and start firing order from that spot like you can on an even fire. Because of this, note the new notch located on the lower right of the picture. Also note the screw holding the pickup in a fixed position; I simply drilled and tapped through the base and used a 1/2" standoff with a dab of epoxy as a new mount. The old postion is just to the left of the screw in the pic:
    [​IMG]

    Why you would want to do this mod?
    1) Non-computer HEI cores are getting scarce. At time of this writing, there was not a single Buick 231 (even or odd) vac advance HEI available at my local DIY salvage yard. By comparison, there were probably 10 or so HEI/ESC units.
    2) You like HEI, but are having vac advance/fan clearance issues. The HEI/ESC distributor uses no vac advance. Added bonus, there is no mechanical advance, so no weight bushings to wear out.
    3) You like tinkering with your HEEP.
    4) You try to recurve your ignition and break off the weight pins 2weeks prior to a trail ride. Necessity is the mother of invention.

    The distributor cost me $27. I don't remember what I paid for the oddfire pickup coil and cap, I just swapped them over from my other unit so they didn't cost me anything this time around, but I think they were maybe $40 or so. Also $.92 for a 1/2" steel standoff at the local Big Orange Box. So, altogether could probably duplicate this project for <$70, basically the same as any other HEI conversion, which is about less than a third to a half of what you'll pay for an oddfire reman.

    Coming soon to an ECJ5 tech thread near you: I was wandering around looking for donors when I discovered a Buick small body HEI/ESC! Coil is mounted separately from cap, but electronics appear same. Basically the same footprint as a Delco unit (no intake grinding!), the same punch as an HEI conversion (arc a big gap), and you ditch the vac advance (no sensitivity issues or need for adjustable unit) all in one fell swoop! Will need to figure out how to get HEI posts onto unit, however, since no small cap oddfire Buick engine was ever produced.
     
    Last edited: Mar 5, 2009
  20. Mar 5, 2009
    bkd

    bkd Moderator Supreme Staff Member 2022 Sponsor

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    bro you deserve this :beer::beer::beer:....nicely done
    Jim S.
     
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