Replacing TBI w/ Carb

Discussion in 'Performance & Fuel' started by bigbluesub, May 18, 2010.

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  1. bigbluesub

    bigbluesub New Member

    Update. Motor is in truck. I unplugged the fuel pump and the mech. pump seems to pull thru the old pump just fine. The fuel gauge is not working though. I am going to close off the return line and see what happens. I was down for quite a while because of rusting out brake lines.
  2. Chris Miller

    Chris Miller New Member 100 Posts

    I wouldn't recommend closing off the return line. It'll probably vapor lock.
    That is rather strange that the fuel gauge isn't working. Did you unplug the fuel pump wires or the fuel pump relay?
  3. bigbluesub

    bigbluesub New Member

    I did close off the return line, I saw that there were two vent lines besides the supply and return lines. Hoping I won't regret it. I unplugged the only wire I saw coming from the Tank, besides the ground. I need to check out a wire diagram to see if the plug was for both the gauge and pump.
    New problem, I let my son take it out Sunday and it went thru 13 quarts of oil. I haven't had a chance to see what is going on there. Sure glad it isnt my daily driver.......

    ---------- Post added at 01:50 PM ---------- Previous post was at 12:41 PM ----------

    I just had a brain storm. The plug has two wires, perhaps one for pump and one for gauge, since there is a separate ground wire. Makes sense to me.......
  4. bigbluesub

    bigbluesub New Member

    Well I cut the white wire and the Gauge now works and the Pump is off.........
  5. RallySTX

    RallySTX New Member 100 Posts

    My friend is installing a 95 tbi block in his 85 burban, both motors are 454. This article has been helpful.
    Brian L.
  6. Brushwolf

    Brushwolf New Member

    I am replacing TBI 454 with another rebuilt Dyno-tuned 454 that came with HEI, Edelbrock 4v intake, 2162 Edelbrock cam and mechanical fuel pump. Have replacement engine bolted in but nothing else hooked up. Vehicle is a 1989 C20 3/4 ton 2wd Suburban. Has a rebuilt 400 TH trans so no problems with computer control for trans or speedo hookup. Have a few questions:

    - can whole Tbi harness be removed? Looks integrated with main harness?
    - need to remove fuel system sender that goes on along with oil pressure sender?
    - will stock fuel filter on frame rail be a problem since designed for higher fuel pressure?
    - know I can use stock pump with regulator, but don't want to. Prefer old school simplicity..
    - omit two sending units about midway along each head?
    - vent fuel tank? Connect return line to vapor canister or ?
    - factory auxiliary cooling fan used a temp sender to activate or is it computer controlled?
    - all my factory gauges should work with senders salvaged off old engine? Oil, volts, temp?
    - what wire on stock harness gets hooked to HEI?
    - installing headers and dual exhaust also. Any sealant needed on gaskets or loktite on bolts?
    - can the cruise control be used, or is it computer controlled?
    - any other issues I am overlooking?
    Last edited: May 19, 2013
  7. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    First off, welcome to GMTC! Second, if you're getting rid of your 454 TBI, I'm interested in buying the actual throttle-body itself and the injectors. PM me if you're willing. Unfortunately I don't have the answers to all your questions, but this should at least get you started in the right direction.

    Unfortunately, the TBI wiring is pretty well integrated into the main engine harness. You can cut back the TBI-only parts of the looms as far as you can, but to eliminate the wiring completely you'd have to either break down the existing harness and rebuild it or replace it with a carb'd harness.

    The stock filter shouldn't be a problem, and neither should the electric pump. The stock TBI pump runs around 15PSI, so you would need to regulate it down, but it's not by much.

    The cruise control should be driven off the DRAC module under the dash assuming it's an electric speedo. That DRAC module is driven from the speed sensor in the tailshaft of the transmission.
  8. Brushwolf

    Brushwolf New Member

    Thanks for reply. Guess I will just tape up extra connectors and wires for the time being then as don't want to break down harness or part with TBI components until I know carb setup works ok. Ran the VIN number through decoder and it says I have 4 speed auto from factory, but if that is true that would have been 700R4 and the trans has been replaced with 400TH. It has a mechanical speedo cable attached to trans and speedo worked so perhaps speedo was swapped out to mechanical unit at the same time? Been raining 4 days so have not got much done lately. Know if the cruise control setup is different between mechanical speedo and electronic speedo? Suppose I could just remove it, but kind of liked having CC on longer drives. Thanks Mike
  9. Hite664

    Hite664 New Member

    Saw this post and thought may you All could help I have a 1990 suburban that I converted from TBI to carbureted and do not have any headlights or dash lights or the radio but have everything else any suggestions on what it could be thank you
  10. BurbanMan

    BurbanMan Member 100 Posts

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