TBI for Chevy 261 straight 6

Discussion in 'Injection Tech' started by lostmy47, Jan 28, 2012.

  1. lostmy47

    lostmy47 Farmall Cub

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    Hi-
    I am in the process of finishing the build on a replacement motor for my 1950 Chevy 1 ton truck.
    Its a 261 straight six bored .080 over to make it 270 or a 4.4L.
    Ive got a Offenhauser dual intake manifold on it and Fenton cast Iron headers.
    There's a slightly hopped up cam in it but this motor is being built for torque not speed.

    I am making decisions on intake now.

    Initially I was going to run single barrel Rochesters, they are the epitome of "vintage" hot rod stuff.
    Since I build and restore vintage motorcycles for people and ALWAYS make them more reliable, I realized how stupid I was being and decided to run 2 progressive 2 barrel Weber carbs. First I was thinking the Holley Webers from the Ford Pinto days, then I thought I'd run 32 36 DGEVs instead.

    Wait I'm getting to the FI part! :punk:

    The distributor for the 261 is shot so I've been shopping for a distributor. A friend asked me if I was going to go with fuel injection on the new engine.
    DUH! I felt like I'd been hit with a hammer. I actually hadn't even thought about it but its a pretty brilliant thought.

    After reading for a couple days I have some questions:
    Is there a small 2 injector throttle body for maybe a 4 cylinder out there?
    Is there a single barrel throttle body out there?
    Injectors are stupid, right? they don't know what system they are hooked up to all they know is "spray" or "rest" right?

    OK I'll start there.

    I like the idea of FI I just want it to run properly without a ton of headaches.

    All Suggestions and Ideas, appreciated. If I decide to do it I'll keep a log here and over at stovebolt.com. So people in both places can get there giggles in. :D

    Jeremy
    San Jose, CA
     
  2. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    To keep things simple for you and the ECM I would recommend using 2- 1barrel throttle bodies. I have a couple writeups in the FAQ's that will show the different styles. But there are many different ones avail.

    The thing to keep in mind is that the injector driver in the ECM is designed for a specific load. So the TBI injector is a peak and hold style injector with a resistance of 1.5ohms.
    The 4.3 V6 TBI system using the 122774 ecm like in the FAQ's here runs a 2 barrel throttle body. So it's designed to run 2 injectors.

    To run on your dual carb manifold you simply run 2 1 barrel throttle bodies like off of a 2.5l (iron duke) 4 cyl from the S10.
    Then you just run 1 injector wire to each throttle body.

    The ECM has no idea and only cares that it is running 2 injectors of the right ohms.

    I have also looked at the little geo metros and they have a 1 barrel TBI but I haven't measured the injector.

    But look under the hood of any GM product with a TBI and you will find many options.

    You know GM actually did this from the factory on the crossfire camaro. It had 2- 1 barrel throttle bodies. I have a couple of them also!!

    The other option is to run a single manifold and run the GM 2.8 or 4.3 V6 throttle body with the same computer.

    Take a look at the 4 cyl writes listed in the FAQ's(start here) for a couple examples.

    HTH
     
  3. lostmy47

    lostmy47 Farmall Cub

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    Thanks Bill!
    That's exactly what I was thinking. Two single injector TBs hooked up to the ECM as if it was a one 2 barrel injector.


    Off to read more...

    Back soon.

    Jeremy
     
  4. BO185

    BO185 High Wheeler

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  5. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    Careful with that.
    Read the GM HEI FAQ.

    Just because people do it does not make it right.

    And he came over here from the stovebolt board!!!!

    Maybe he was looking for the correct information!:D
     
  6. BO185

    BO185 High Wheeler

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    Yes I Should have stated it better. I believe the last year 292's had big body 7-pin modules.

    Here's one. http://www.stovebolt.com/techtips/hei_conversion.htm
    Also you could mount the module outside the HEI.
     
  7. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    Yep, That's the one that doesn't work so well with EFI.
    You need to look at the HEI FAQ.
     
  8. lostmy47

    lostmy47 Farmall Cub

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    I came over here to find what others had done and made work.
    I see this as a way to stay interested in getting this project of mine finished! LOL :clap:

    So BO185, did you get any further?

    Jeremy
     
  9. BO185

    BO185 High Wheeler

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  10. lostmy47

    lostmy47 Farmall Cub

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    Bill has me thinking that a pair of those 300CFM Holley TBs may be the answer?
    That and a v6 TBI system.

    I saw that the adapted distributor didn't work because it was rotating the wrong way, but I didn'T see the gm hei FAQ..

    I may be blind.

    Jeremy
    FNG :yes:

    San Jose, CA
     
  11. Bill USN-1

    Bill USN-1 Moderator Staff Member Moderator

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    Here's the HEI FAQ.
    http://www.binderplanet.com/forums/showthread.php?t=46961

    The issue isn't really that they turn the opposite dirrection, although there are some olds ones that do. it's that the reluctor phasing is more inline with the cap terminal then past it.

    if you can find one of the later big cap distr with the 7 pin module already in it.
    If it was already designed for EFI then it will work fine.

    You can convert one of the 4 pin distr like in the faq and with the older engine you probably won't need to optimize the timing so it may work fine for your application.
     

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