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2.8l to 4.3l engine swap

Discussion in 'Chevy S10 Forum (GMC Sonoma)' started by chriscolehawk, Apr 15, 2014.

  1. chriscolehawk

    chriscolehawk New Member

    2.8l to 3.4l engine swap

    1985 GMC S15 2.8l v6 2wd Ext cab auto.

    I have decided to just go ahead and go with the 3.4l V6 engine because I've read that it is a direct fit. My only issue now is I have an automatic and would prefer to have a 5-speed manual. Does anyone know if it will be a direct fit or if any modifications will be needed?

    I'm also under the assumption that everything from my 2.8 will bolt up to the 3.4. Alt, Intake, A/C
    Any and all help will be greatly appreciated.
    Thanks! =-=-Chris=-=-
    Last edited: Apr 16, 2014
  2. Gramps43

    Gramps43 Member 1 Year

    I don't think they are compatible, the 2.8 is a 60° engine and the 4.3 is a 90° in the SBC family of engines. As for as accessories are concerned the Alt, A/C and P/S should work with the appropriate 4.3 brackets.

    Disregard the above, me BOO-BOO.
    Last edited: Apr 19, 2014
  3. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    I don't think your auto tranny will bolt to the 4.3 bell housing, I think the bolt hole pattern is different.
  4. BurbanMan

    BurbanMan Member 1 Year 500 Posts

    A 3.4 will work. A 4.3 will work if you get different motor mount perches. You will need another tranny, harness, computer. I did this swap with mine except I started with the 2.5. You will need a harness/computer regardless. A 2.8 v6 5speed will bolt up to the 3.4, but I believe you will need another 5 flywheel. That I can not be certain about,
  5. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    My bad, I said the bell housing would be different, the 3.4 should be the same, I was thinking and typing 4.3

    EDIT: is it just me, or is there something strange about the heading on the 1st post.

    When closed it shows 2.8 and 4.3, but when opened, it shows 2.8 and 3.4. What's with that?
  6. Gramps43

    Gramps43 Member 1 Year

    Actually no there's nothing wrong, but there is a problem with my eyes. The 3.4 is the last of the 60° V6's so everything from a 2.8 and a 3.4 should swap.
  7. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    No gramps, you made the same error I did. It reads 4.3 when the thread is closed and it reads 3.4 when the thread is open.
  8. Gramps43

    Gramps43 Member 1 Year

    Damn I wish I could make up my mind. 8~{)) Where is the guy who started this mess when you need him. When he does show up I'm going to rumble all over hi butt. 8~{))
  9. chriscolehawk

    chriscolehawk New Member

    Sorry for all the confusion. When I made the post I typed 4.3 instead of 3.4. I went back and edited it.
    Now, heres a few questions..
    My truck is not computer controlled.. (I assume because there is no check engine light.) Am I right?
    Also the 2.8 has the mechanical fuel pump and is carburetor. Does the fuel pump mount the the 3.4?
    Last edited: Apr 19, 2014
  10. BurbanMan

    BurbanMan Member 1 Year 500 Posts

    the 3.4 is fuel injected. You will need to install a computer and wire it all up.

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