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Thread: Hello, new guy here searching for TBi info

  1. #1
    Carb and Points!
    Join Date
    May 2014
    Location
    Alabama
    Age
    56
    Posts
    1

    Hello, new guy here searching for TBi info

    Hey all.


    I am having issues with an efi system and ran across this site. Cool. I do not have any specific questions yet but plan to use the search button extensively as a start.


    My project started out as trying to get an engine rebuilt for my wife's 1993 Chevy Stepside with 5.7 TBI. It has seen better days cosmetically but all our children came home in it after they were born so the plan is to keep it. Personally I either want it or one like it as my backup daily driver. While investigating a rebuild I found out a local builder could sell me a rebuilt vortec for only $150 more than the tbi motor so......only $150 more for roller cam and better heads?......and the project creep began.


    The engine has been rebuilt and installed along with an edelbrock intake, holley tbi plate adapter, new higher pressure higher volume fuel pump, and a tbichips chip(apparently my first big uh-oh). It idles OK but spits back through the intake between 2500-3000 rpm. I gotta do some reading to see if I want to buy the stuff to try to tune it myself or just get some forum recommended person to make a chip for me.


    My mechanic told me the fuel pump was making 60psi and the tbi regulator spring is not strong enough so extra fuel is getting dumped in. He is running it on an 18psi source from outside the vehicle at the moment. I think I may need an extra pressure regulator to drop the pressure closer to 18-20psi before it goes in the tbi unit. The spring in the tbi regulator is supposedly a new 18psi version.


    Feel free to offer advice but I will wait to officially request any until I can learn a little more.


    Rob
    Rob
    1987 BMW 535is
    2003 GMC YukonXL
    1997 GMC Suburban
    1993 Chevy Stepside 5.7 Vortec TBI in progress

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    6,268


    I'm curious about the fuel pressure. Myself and several other members have installed TPI fuel pumps (or equivalent higher pressure / flowing pump) instead of the original TBI fuel pump. A proper functioning TBI fuel pressure regulator will maintain the stock pressure ( usually 11 ~ 13 PSI) with a higher pressure / flow fuel pump. To my knowledge, the only way to increase pressure from a TBI pressure regulator is increase spring pressure. Compressing the stock TBI regulator spring will net a small increase in fuel pressure to about 15 PSI.

    I've done considerable research on the TBI pressure regulator, here is a link to some of the research I shared. http://www.gearhead-efi.com/Fuel-Inj...rings-Measured

    dave w
    Last edited by dave w; 05-24-2014 at 04:53 AM.

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