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 New Member

    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 Active Member

    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

    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 Active Member

    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 New Member

    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 Active Member

    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 New Member

    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

    the 3.4 is fuel injected. You will need to install a computer and wire it all up.
  11. Gramps43

    Gramps43 New Member

    I wouldn't worry about fuel pumps, a good electric pump and a pressure regulator for carb'd engines aren't that expensive and would probably perform better in the long run. As far as I can tell 3.4's were EFI but as you are only going to use the short block that should matter. Go forth and play happy. 8~{))
  12. chriscolehawk

    chriscolehawk New Member

    Could I not just installed the intake and carb from the 2.8 and make a fuel pump work with it?
    I planned on buying the 3.4 crate long block, swapping everything over and putting it in..
  13. Gramps43

    Gramps43 New Member

    Well yeah I reckon you could but you would also have to transfer the ignition system over as well because the 3.4 is computer controlled. You might be better of to just swap in the whole 3.4 with ECM and harness, then get a stock 3.4 fuel pump. Hook up the power, do the plumbing let her rip. Or you could locate a donor vehicle with a good running 4.3 "w" code in it that has been rear ended or totaled without involving the engine and swap it over lock, stock and barrel. Then you'll have plenty of go power.
  14. chriscolehawk

    chriscolehawk New Member

    I don't mean to be a pain in the ass, but what would I need the computer for? If the engine was designed to be a replacement engine for the 2.8 why couldn't I just mount everything up from the 2.8 and go?

    - - - Updated - - -

    I have short time frame to swap the engine. The 2.8 is starting to smoke and I'm wanting more power, not a lot more but just a little more then the 2.8 has.

    Its also v-belt setup.. Is this going to effect anything if its even possible with what I'm trying to do without a computer?
  15. Gramps43

    Gramps43 New Member

    There's nothing stopping you, my grey cells were just spasing out. As long as you get the fuel and ignition systems from the 2.8 I think it should work. At the outside you might have to get an after market distributor but like I said that's at the far outside. I just happened to think you will have to do a little work on the carb jets so it can properly feed the larger displacement. You don't want your new engine to run lean and burn a piston.
  16. BurbanMan

    BurbanMan Member

    i agree. You will still need an aftermarket electric fuel pump as the 3.4 does not have an engine mounted pump. No biggie there as they are fairly inexpensive. You will need a bigger carb. Holley makes a great 300-350 cfm 2 barrel that would work great. If you want to get more oomph and better mileage, install an adapter plate And run their 350cfm 4 barrel. With a tuned 4 barrel, you would also get better mpg. 8) tell me that is not a plus!
  17. RayVoy

    RayVoy Active Member

    There is a good chance you will not be able to use the distributor either. The block may not have a hole and the cam will not have a gear to drive the dist shaft.
  18. BurbanMan

    BurbanMan Member

    thats an excellent point.
  19. chriscolehawk

    chriscolehawk New Member

    Great bit a help here!! Thanks a bunch.
    Now I'm crying about this damn distributor. I'm calling about buying the engine soon and I'll check with them to see if it will work for me.
  20. BurbanMan

    BurbanMan Member

    see if he has the wire harness and computer too. It wouldn't take much longer to tuck the wiring and mount the computer behind the glove box or under the pass seat

Share This Page