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Thread: Ford six F.I. on a GMC inliner?

  1. #1
    Carb and Points!
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    Ford six F.I. on a GMC inliner?

    Just checking out possibilities-How hard is it to use a Ford 300 six fuel injection set up on another six? I'm looking for a way to set my 302 GMC six up with fuel injection,and thought the 300 inch Ford six set up might be an easy way to do it,plus it's close enough in size to not require much tuning to run well. I'm assuming the F.I. needs a higher pressure fuel supply,it may need a special distributor and possible a bunch of wiring and sensors;is it even possible to convert it into an old truck like my '54 GMC?
    Another option I'm looking at is a TBI from a Chevy 305,but I'm not sure how to make an 8 cylinder system work on a 6 cylinder engine. Maybe a 4.3,but I'm told none of those were fuel injected. I guess the question is,how would YOU go about it?
    Speed

  2. #2
    Super Moderator dave w's Avatar
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    I have experience doing EFI conversions and tuning. What I would do might not be an easy or low cost option for you?

    I'm not familiar enough with the GMC 302 six cylinder, so I would first need to first figure out what is needed to get an EFI 8 pin ignition module working in the GMC 302 six cylinder distributor. Once I got the distributor using an EFI 8 pin ignition module, I would use the GM TBI system from a V8. I would modify and tune the PROM chip programming for a 302 six cylinder.

    dave w

  3. #3
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    TBI is probably the easiest choice. The old Jimmy sixes are three port engines and the firing order causes uneven pulsations from the different ports. PFI on a three port manifold could cause unequal fuel distribution. I'd probably attempt to design an intake with dividers that extend into the head if possible in order to facilitate a port conversion.

  4. #4
    Carb and Points!
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    I'm inclined to agree on that;the plan I was thinking of would be mounting a TBI on the stock intake (Since it's already a 3 bolt 2 barrel,like an old Stromberg 94 or 97,it'd just be a matter of making an adapter plate.),and I know I can modify a later GMC or Chevy straight six distributor,(even an HEI) to work in this engine. My biggest concern was finding a straight six distributor that's compatible with EFI,but it now sounds like I'll have to "build" one. Can the 8 pin module be mounted externally? There's not a lot of room inside those distributors. I assume I'd make the distributor fit the GMC block then use an EFI distributor for a model to fit the newer components. I know (I THINK) I'd have to get the ECM from whatever I get the module etc. from,all the wiring that relates to it,and most of the sensors etc. I was told earlier by a guy who installed TBI on an older Chevy truck I'd only need something like 5 wires from the harness and a couple of the sensors to make it run,due to not having all the electronics to wrestle with,is that right? (Sounds TOO simple to me.)Whatever happens,once it gets to the "modify and tune the PROM chip" segment,I'll have to farm that out. I don't have the tools,or the brains,to get into that. Speed

  5. #5
    Super Moderator dave w's Avatar
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    The 8 pin HEI module can be mounted outside the distributor. Using the Ford type pickup coil can save space under the distributor cap. The pictures show the 4 pin HEI module, which is similar in size / mounting to the 8 pin HEI module.

    With some careful planning, the original distributor can be modified like the distributors shown in the pics below.

    dave w

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    There are definitely 6 cylinder TBI setups right out of GM. The 4.3 engines came in TBI in both cars and trucks and they were equipped with a distributor. The early distributor uses the same electronic ignition system as the carbureted HEI engines with four additional pins to communicate with the computer. There were also 2.8 TBI engines which were six cylinder and distributor equipped. If you can adapt an HEI distributor then you can substitute the 4 pin HEI module for 7 pin HEI module from a CCC equipped vehicle such as a Carquest 55-1541.

    At the computer end, if you have an early computer you need to get a six cylinder chip to put inside. If you have a later computer you'll need a six cylinder memcal. Neither is impossible to find.

    What's nice about using a computer for the ignition is that you can get exactly the timing you need at a specific load and rpm. It can make the engine respond so much better overall.

  7. #7
    Carb and Points!
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    Okay-I see what we're doing now. Now,the NEXT dumb question;What engines do I need to source what parts from? I have a Chevy six HEI distributor I've already modified to fit the 302 GMC motor;will this work as a base for the 8 pin module and related components?
    Speed

  8. #8
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    sounds like youre halfway there with the dizzy simple module swap and its ready

  9. #9
    Carb and Points!
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    Cool-so if I use the big distributor does the 8 pin bolt in where the original was or do I need to drill new holes etc.? Then,what ECM would I need-the one that went with the TBI unit I plan to use?
    Speed

  10. #10
    Super Moderator dave w's Avatar
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    The 4 pin module and 7 pin module will fit in the same holes. (Top two modules in the pic below)

    7 Pin Module is used with a Large Cap HEI that has the ignition coil in the cap.

    8 Pin Module is used with a Small Cap HEI that has a remote mounted ignition coil.

    dave w
    Last edited by dave w; 12-10-2014 at 12:16 AM.

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    ^^ Nice picture! Very good comparison.

    Quote Originally Posted by Speedking View Post
    Okay-I see what we're doing now. Now,the NEXT dumb question;What engines do I need to source what parts from? I have a Chevy six HEI distributor I've already modified to fit the 302 GMC motor;will this work as a base for the 8 pin module and related components?
    Speed
    You may need to cut a small notch into the distributor to accommodate a plug for the additional wires to the computer. The part number I gave is an aftermarket module and it's used for both six cylinder and eight cylinder engines. The OEM listed different modules. Originally, large cap HEI distributors with clockwise rotation and 7 pin modules were found on 229 Chevrolet engines and 238 even fire Buick engines with CCC systems (computerized carburetor) from around '81 to roughly '84. You may be able to use a 7 pin module from a V8 car. There are likely to be some differences in dwell time and spark advance when the computer is not controlling timing, at least with the OEM parts. But it may not be noticeable. I would expect the V8 wiring harness could be made to work in a pinch although I really try to get everything from the original applications because you just never know what subtle differences you'll find.

  12. #12
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    Quote Originally Posted by 1project2many View Post
    ^^ Nice picture! Very good comparison.


    You may need to cut a small notch into the distributor to accommodate a plug for the additional wires to the computer. The part number I gave is an aftermarket module and it's used for both six cylinder and eight cylinder engines. The OEM listed different modules. Originally, large cap HEI distributors with clockwise rotation and 7 pin modules were found on 229 Chevrolet engines and 238 even fire Buick engines with CCC systems (computerized carburetor) from around '81 to roughly '84. You may be able to use a 7 pin module from a V8 car. There are likely to be some differences in dwell time and spark advance when the computer is not controlling timing, at least with the OEM parts. But it may not be noticeable. I would expect the V8 wiring harness could be made to work in a pinch although I really try to get everything from the original applications because you just never know what subtle differences you'll find.
    I may be late to this party, but why not just use the CCC HEI from a 4.1L I6 from say a California model of a 1984 G20 van?? I believe it is AC Delco # 88864755

  13. #13
    Carb and Points!
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    "I may be late to this party, but why not just use the CCC HEI from a 4.1L I6 from say a California model of a 1984 G20 van?? I believe it is AC Delco # 88864755 "
    I'll check that out;I'm discovering several different shaft lengths,depending on what I use. A late 70's 250 distributor is too long and needs the the shaft cut and re-shaped to drive the oil pump,and needs the drive gear moved and drilled and re-pinned. I have an HEI distributor from a 4.3 (?),but it's just too short. Then I have a points distributor from an early 70's 292 that's only about 1/4 inch too short;not sure WHAT to make of THAT. It appears whatever distributor I choose will need to have the housing modified at the base,the shaft will need to be lengthened or shortened,the end will need to be cut to a "blade" style to match the oil pump,the drive gear will need to be moved and/or replaced,and it may be necessary to be "creative" with fitting a suitable module and wiring.
    "I really try to get everything from the original applications because you just never know what subtle differences you'll find."
    I'm with ya on that.
    More measuring,re-designing,configuring and wondering why I decided to do this will be ensuing.
    Thanks for all your help,ideas and information-none of it will go to waste. The truck is currently about 15 miles away,stricken down with some burnt wiring (THANKS,mice!),but I have what parts I need to retrieve it. I'll be doing that as soon as the ground firms up enough to drive it out.
    Speed

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