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Thread: distributor and wiring question

  1. #1
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    distributor and wiring question

    Hello, I grabbed a complete engine harness (well I forgot the aldl (or however its spelled) connector so I'll have to go back for that) and ecu from a 1988 truck. it was a 1988 truck and from the code on the ecu the truck was apparently a 4.3 (engine was gone but harness was carefully taken apart making me think they would be coming back for it). ECU was code AKDW. I also grabbed a ARHT ecu from a 92 truck as it was just dangling there. I compared it to a 1989 wiring diagram found online and something didnt look right but going by the sticky thread in here, the diagram looks to compare properly to mine?

    http://www.gearhead-efi.com/Fuel-Inj...5ur6hLR8uzeETA



    I have a v8 distributor but the internal wires are different colors from the diagram. also, they are kinda hard and shiny wires, are they shielded?


    ultimately, all of this will go into a 59 chevy apache with a 235 engine. nobody makes a TBI distributor for this engine and dave's small body HEI hasnt been communicating lately (hopefully he is well), so I plan to make my own as I want the ecu to control timing using the 4.3 ecu.

    the plan is this:
    1. HEI vac advance dizzy from ebay https://www.ebay.com/itm/26348431495...Bk9SR4ilmLzfYQ

    2. remove vac advance and lock out the mech advance (will probably JB weld or something as I dont have an actual welder).

    3. use the pickup wires in the HEI dizzy to connect to the 8pin TBI module I rob from the v8 dizzy I have.

    reading this page:
    http://www.megamanual.com/ms2/GM_7pi...93F5B927yx98Qs

    I guess I will need to reverse the wire hookup on the ebay dizzy compared to the factory TBI dizzy? correct? or am I reading it wrong?
    will my idea even work? I dont want to do any machining which is why I will just modify the pre-existing ebay HEI. I searched on here and didnt see anything similar and every time I try to use a 3-character search I get no results so I guess thats too short of a search term?

    I guess my other two distributor questions are that the ebay dizzy appears to be a 3 wire setup from the picture (red/yellow/black). can I even use its magnetic pickup for the tbi module? I'm guessing there is some weird extra tach wire or something?

    per the wiring diagram, the only modules/sensors I'll need are coolant temp, TPS, MAP, IAC, o2 sensor, TBI distributor module. I have a bracket from the 92 v8 truck (it still had the engine) that has the map sensor, the ecs sensor, and some other sensor on the back of it. I assume the IAC/TPS and maybe the coolant temp sensor are on the throttle body itself? I didnt grab the one from the truck as the injectors were missing and I already have a TB hiding somewhere in my garage.

    what external inline fuel pump would be good to use for this?

    some of my idea came from here:
    http://67-72chevytrucks.com/vboard/s...d.php?t=337554
    https://www.youtube.com/@drummin52/videos
    Last edited by stackz; 03-20-2023 at 12:41 AM.

  2. #2
    Super Moderator dave w's Avatar
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    The YouTube video showed a large cap HEI.

    Some mid 80's California emissions I-6 250 Cubic Inch six cylinders used large cap HEI distributors without vacuum advance and 7 pin HEI ignition modules.

    Perhaps AC DELCO part number 88864755 is an option? ACDelco Distributor 88864755 | O'Reilly Auto Parts (oreillyauto.com)

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    Quote Originally Posted by dave w View Post
    The YouTube video showed a large cap HEI.

    Some mid 80's California emissions I-6 250 Cubic Inch six cylinders used large cap HEI distributors without vacuum advance and 7 pin HEI ignition modules.

    Perhaps AC DELCO part number 88864755 is an option? ACDelco Distributor 88864755 | O'Reilly Auto Parts (oreillyauto.com)
    The Mexican TBI ones used the 7 pin as well into the 90s GMT400s. Not sure what the port injected 250s used as they had some form of Bosch controller and mass air. I want to say the later 90s up to 2000ish used the 3800 waste fire coils though.

    The TBI I6 I setup years ago in a 37 Chevy had dual 1bbl TBIs on a dual carb manifold.
    Last edited by Fast355; 03-20-2023 at 05:07 AM.

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    the only thing for that is I havent found anyone who can tell me what the modifications that are needed to be done to convert a 250 dizzy to work on a 235. I have found the 250 TBI units online but cant find even an HEI one just to grab for cheap and bring home to compare them with my spare points 235 dizzy side by side. Thats why I'm thinking just buy the 235 HEI one and modify it to work. my hang up on THAT one is that it looks like 3 or 4 wires are coming out of the thing. a guy on the stovebolt facebook page has one he hasnt installed yet so he's going to take a pic of the guts for me so I can see how many wires are coming out of the magnetic pickup. If there's only 2 then I'd be willing to pay the $100+ to mess with it. but if its got something goofy like 3 wires coming out of the pickup it'll just be me throwing money at the wind.

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    Quote Originally Posted by dave w View Post
    The YouTube video showed a large cap HEI.

    Some mid 80's California emissions I-6 250 Cubic Inch six cylinders used large cap HEI distributors without vacuum advance and 7 pin HEI ignition modules.

    Perhaps AC DELCO part number 88864755 is an option? ACDelco Distributor 88864755 | O'Reilly Auto Parts (oreillyauto.com)
    curiosity got the better of me so I looked at it. saw it has the same external 3 wires as the 235 ebay HEI. put in the part number on google and found it on gm parts direct with additional pics. it gave me an overhead shot of it.
    7c6452328628320aeb5358537f3f3c02.jpg

    nice. same 2 wire internal pickup as the v8 TBI dizzy I have at home. I'm hoping I see the same when the facebook guy takes a pic of his. if so, I'm just gonna go ahead and grab one and run with it. wont have to worry about any type of machining, etc. just cutting as I'll gut it and then cut the side opening some to fit the TBI module to the old vacuum housing. I've read I'll need to use thermal paste or I'll burn up the module which I've got a bunch of. I'm wondering why the ac delco one has that resistor (or condensor...looks like a points condensor...for noise cancellation like on ford TFI maybe?) in it? and if I would need it with the 8pin module. I dont see one in the dizzy I have but it may be somewhere else in the system originally.

  6. #6
    Super Moderator dave w's Avatar
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    The TBI ECM will work with either 8 pin or 7 pin Ignition module.

    The 7 PIN Module is a Super Simple Solution - It can't get any easier or any less complicated.

    Others might not have known how simple it can be to TBI an I-6 six cylinder engine If they would have only known.

    HEI.PNG

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    Quote Originally Posted by stackz View Post
    curiosity got the better of me so I looked at it. saw it has the same external 3 wires as the 235 ebay HEI. put in the part number on google and found it on gm parts direct with additional pics. it gave me an overhead shot of it.
    7c6452328628320aeb5358537f3f3c02.jpg

    nice. same 2 wire internal pickup as the v8 TBI dizzy I have at home. I'm hoping I see the same when the facebook guy takes a pic of his. if so, I'm just gonna go ahead and grab one and run with it. wont have to worry about any type of machining, etc. just cutting as I'll gut it and then cut the side opening some to fit the TBI module to the old vacuum housing. I've read I'll need to use thermal paste or I'll burn up the module which I've got a bunch of. I'm wondering why the ac delco one has that resistor (or condensor...looks like a points condensor...for noise cancellation like on ford TFI maybe?) in it? and if I would need it with the 8pin module. I dont see one in the dizzy I have but it may be somewhere else in the system originally.
    hmm, well I asked a question to the seller for the small cap HEI:
    https://www.ebay.com/itm/32555572834...&segname=11051

    he responded with an item number saying it had a circuit board in it and not a module, something tells me the small cap units are out lol:
    https://www.ebay.com/itm/32237765735...Bk9SR9KfsZTgYQ

    hopefully when I hear back from one of the large cap HEI sellers I get better news.

    edit: he said the large cap HEI distributors he sells use the standard HEI module so yay for that! sounds like a winner winner chicken dinner to me.

    whats the difference between the 7pin and 8pin module? it looks like they do the same thing? just that the 8 pin has a "G" terminal on it? is this an extra ground? I wonder why it has an extra ground?
    Last edited by stackz; 03-21-2023 at 02:28 AM.

  8. #8
    Super Moderator dave w's Avatar
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    The 7 pin module has the coil internally mounted inside the Distributor Cap.

    The 8 pin module has the coil externally mounted outside of the cap.

    The standard 4 pin HEI module is not a good TBI option in my thinking, more like keep banging head on wall and wait for the chicken dinner to hatch.

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    Quote Originally Posted by dave w View Post
    The 7 pin module has the coil internally mounted inside the Distributor Cap.

    The 8 pin module has the coil externally mounted outside of the cap.

    The standard 4 pin HEI module is not a good TBI option in my thinking, more like keep banging head on wall and wait for the chicken dinner to hatch.
    yup, and the guy on ebay said the large cap HEI dizzy comes with the 4-wire module. doesnt bother me. it just means it uses the same pickup as OEM which means I dont have to do any machine work at all. All I have to do is open it up, lock out whatever vacuum/mechanical advance is present, toss in and mount/wire up one of the 8pin modules I already have, and wire in the internal HEI coil, and be happy. I'm stoked I dont have to have a custom distributor made or do any machine work, etc.

  10. #10
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    Quote Originally Posted by stackz View Post
    yup, and the guy on ebay said the large cap HEI dizzy comes with the 4-wire module. doesnt bother me. it just means it uses the same pickup as OEM which means I dont have to do any machine work at all. All I have to do is open it up, lock out whatever vacuum/mechanical advance is present, toss in and mount/wire up one of the 8pin modules I already have, and wire in the internal HEI coil, and be happy. I'm stoked I dont have to have a custom distributor made or do any machine work, etc.
    Yep, the 7 pin module is plug and play right out of the box, no machine work, no vacuum advance to lockout . . . just miles and miles of smiles.

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    Quote Originally Posted by dave w View Post
    Yep, the 7 pin module is plug and play right out of the box, no machine work, no vacuum advance to lockout . . . just miles and miles of smiles.
    just curious. whats the best (easiest way) to lock out the vacuum advance? just remove it? I dont have it in hand right now but I assume that as it sits without being in a car as-is any vacuum advance and/or mechanical advance is going to be at base timing internally so lock it where it is? then the ecu can control all the timing however it wants once installed and running.

    and I guess...if factory on my 59 235 base timing is 10 BTC. set this distributor up the same? or do I set it at 0BTC (top dead) or something weird?

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    ok, I ordered one of the large cap HEI distributors off ebay. should be here next week so I can then open it up and have a look at it.

    looking back at this page:
    http://www.megamanual.com/ms2/GM_7pi...93F5B927yx98Qs

    the 7pin module is part number LX315, looking it up on rockauto shows me a ton of things it actually came in. once I get the new dizzy here and confirm it has the 4-pin, I will likely use the info I have to hit up the u-pull yard so I can grab a couple 7pin modules and the 5 pin connector harness for dirt cheap.

    I'm wondering if there is a male side connector (module side) for the TBI 8pin harness? would rather leave the engine harness I have intact and make a modified connector if possible from the 3 timing pinouts on the 7 pin to the 4pin of the 8pin. here a pin, there a pin, everywhere a pin pin. haha.

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    Super Moderator dave w's Avatar
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    If I remember correctly, the 7 pin module and 4 pin module have different bolt patterns.

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    Quote Originally Posted by stackz View Post
    the only thing for that is I havent found anyone who can tell me what the modifications that are needed to be done to convert a 250 dizzy to work on a 235. I have found the 250 TBI units online but cant find even an HEI one just to grab for cheap and bring home to compare them with my spare points 235 dizzy side by side. Thats why I'm thinking just buy the 235 HEI one and modify it to work. my hang up on THAT one is that it looks like 3 or 4 wires are coming out of the thing. a guy on the stovebolt facebook page has one he hasnt installed yet so he's going to take a pic of the guts for me so I can see how many wires are coming out of the magnetic pickup. If there's only 2 then I'd be willing to pay the $100+ to mess with it. but if its got something goofy like 3 wires coming out of the pickup it'll just be me throwing money at the wind.
    How to modify 230 / 250 / 290 HEI distributor for use in a 235
    https://www.trifive.com/threads/will...n-a-235.53614/
    https://www.jalopyjournal.com/forum/...ersion.189074/

    Aftermarket 230 / 250 / 290 HEI distributor
    https://www.speedwaymotors.com/Chevy...ck,455337.html

    Converting pre-computer HEI to computer controlled HEI. Includes instructions for removing mechanical and vacuum advance.
    https://www.binderplanet.com/forums/...ersion.128469/

    The magnetic pickup uses two wires. Green and white or green and yellow. Old HEI, before computer control, only had three wires coming out of the distributor to the cap and one or two from vehicle to cap. Computer controlled has 5, 6, 7 or 8 wires depending on the system and the year. You will use a 7 pin module for your HEI conversion. The HEI distributor used for your TBI swap will have four wires to connect to the ecm and will have three wires to connect to the cap. The cap wires will include power, coil-, and tachometer. You will need to supply power to the cap from the vehicle harness. If you use a tachometer it will likely connect to the cap as well. The module in the distributor linked above will need a notch cut into the side to accomodate the four wire harness that connects to the ECM. The distributor will need to have additional modifications so the 7 pin HEI can be attached to the distributor housing.

  15. #15
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    Quote Originally Posted by 1project2many View Post
    How to modify 230 / 250 / 290 HEI distributor for use in a 235
    https://www.trifive.com/threads/will...n-a-235.53614/
    https://www.jalopyjournal.com/forum/...ersion.189074/

    Aftermarket 230 / 250 / 290 HEI distributor
    https://www.speedwaymotors.com/Chevy...ck,455337.html

    Converting pre-computer HEI to computer controlled HEI. Includes instructions for removing mechanical and vacuum advance.
    https://www.binderplanet.com/forums/...ersion.128469/

    The magnetic pickup uses two wires. Green and white or green and yellow. Old HEI, before computer control, only had three wires coming out of the distributor to the cap and one or two from vehicle to cap. Computer controlled has 5, 6, 7 or 8 wires depending on the system and the year. You will use a 7 pin module for your HEI conversion. The HEI distributor used for your TBI swap will have four wires to connect to the ecm and will have three wires to connect to the cap. The cap wires will include power, coil-, and tachometer. You will need to supply power to the cap from the vehicle harness. If you use a tachometer it will likely connect to the cap as well. The module in the distributor linked above will need a notch cut into the side to accomodate the four wire harness that connects to the ECM. The distributor will need to have additional modifications so the 7 pin HEI can be attached to the distributor housing.
    that last write-up is exactly what I was looking for. it was kind of confusing at first as he apparently pieced it together from a couple distributor builds and I didnt pick up on that at first haha. I see a pic with mech advance springs removed...then suddenly they are back again...like wtf? its also confusing because both of the pics showing the "bracket" he created, they are both different length brackets. one its screwed down super close to the housing mount...the other, it looks to be almost an inch away from the housing mount and he cut off the excess of the bracket.

    my HEI is stuck in shipping in Charlotte the past couple of days so I dont have it in hand but I'm curious why he completely removed the vacuum advance unless its for asthetics? I mean if you dont hook it up, it wont be used right? its just kinda sitting there? or do I have it backwards in my head? that its at 0 advance unless it sees engine vacuum?
    Last edited by stackz; 03-28-2023 at 03:03 PM.

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