4.3 TBI to 5.0 TBI question

Discussion in 'Engine Performance + Maintenance' started by Matt Conner, Oct 25, 2019.

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  1. Matt Conner

    Matt Conner I'm Awesome

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    So I got a 1990 GMC 1500 with the 4.3 TBI with the 5 speed. Loosing a lot of coolant through the Exhaust, don’t know if it’s head gaskets or intake gaskets, but I’m trying to come up with a plan B just in case the 4.3 is clapped. I need to know if I got a 5.7 complete with the throttle body and everything. I know I’ll need to change the motor mounts and I’ll need the 5.7 flywheel and clutch, but I don’t know what all I need for the wiring and ECM, so if anyone has some suggestions about all that needs to be done please, reply to this thread, I can provide more info if needed
     
  2. Matt Conner

    Matt Conner I'm Awesome

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    Forgot to mention it’s a 4x4
     
  3. smdk2500

    smdk2500 I'm Awesome

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    You will need to pretty much replace all of the cooling system as well. If i remember right you can reuse your harness but might have to extend some of the wires. You will have to change the ecm.
     
  4. Matt Conner

    Matt Conner I'm Awesome

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    I planned on the radiator and water pump and all that, and I’ll need a 350 ecm if I’m correct
     
  5. Matt Conner

    Matt Conner I'm Awesome

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    I’ve also heard I can reuse the computer in the truck by changing the chip out, I have a engine already but no computer and I don’t want to have to do the wiring harness or anything like that, I don’t have the knack for electrical
     
  6. vr1967

    vr1967 Newbie

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    While the tbi from the 4.3 and 5.7 (and 5.0) will bolt to rack engine, the injectors flow at different rates and need to be swapped per engine size.
    The 7.4 tbi has larger throttle bores than the above engines, but can be made to work.
     
  7. Matt Conner

    Matt Conner I'm Awesome

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    If I
    if I were to get a throttle body from a 5.7 with injectors and all would the fuel lines screw right in? Also I’ve heard there and a few small differences like the knock sensor, I don’t know what the difference is, but I heard there is one. Will the plugin from the 4.3 knock sensor plug into the 5.7 knock sensor? If not can the plugin be changed?
     
  8. Matt Conner

    Matt Conner I'm Awesome

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    I confirmed the leak is the head gaskets, so I’m buying a crate TBI 5.7 and I’m going to swap it
     
  9. Matt Conner

    Matt Conner I'm Awesome

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    I
    I have another question, what ecm model do I need, or what prom chip do I need because I need one for a manual not an automatic
     
    Last edited: Oct 26, 2019
  10. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Do you have a 1227747 ECM (most common for these trucks)? That'll work with a BCC for the V8 and stick shift.
    http://www.gearhead-efi.com/gearhead-efi/bin/1227747/

    Or you can go with the EBL FlashII and play with it yourself. This is a better option if you plan to build up your engine.
    https://www.dynamicefi.com/EBL_Flash.php

    Yes you'll need a Knock Sensor (not sure if the connector is the same), and a Throttle Body from a 5.7L or at least the correct injectors (get flow matched ones)
    http://www.gearhead-efi.com/Fuel-In...1-GM-TBI-Injector-size-color-and-part-numbers
     

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