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Thread: 1992 GMC new motor needs to be tuned

  1. #1
    Carb and Points!
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    1992 GMC new motor needs to be tuned

    Hey,

    I am new to the site. I have a 92 GMC Sierra 1500 5.7. Just got the new motor and trans put in. Motor bored to a 355 converted to a Roller Cam motor with:
    Stock 96 Vortec Heads studded but unported
    Comp Cams Complete Kit with the 258HR Cam
    SpeedPro Forged Pistons
    Stock Crank (Turned 10/10) stock reconditioned rods
    Comp Ultra ProMangum Roller Rockers
    Stock tbi, just cleaned it up
    Stock Computer
    Magnaflow Spun Catalyic Converter
    Magnaflow 3in in/ 2 1/2 outs
    Stock 3.42 gear
    Rebuilt with better clutches and bands and bigger drum 700r4 Trans
    Stock Converter

    High Performance In-Line Electric Fuel Pump12 Volt
    12-17 PSI
    50-58 GPH (190-220 LPH)
    Inlet/Outlet: 5/16" Barb


    I am very impressed with the build first off. Truck runs good when it is warmed up. I notice it stumbles in 2nd when I am on the gas at quarter throttle. Not sure if it's good too much gas or not enough. The truck moves good when I am around 50 mph and above. My fuel pump is listed above. I figured I need a tune. I though about Jets Custom Chip. They said $500 since I changed the Cam. My mechanic said I need a Dynotune to get the bugs out.

    What do you'll think? What should my next steps be? It is my daily driver. I want to clean up issues and make it run clean and open throttle.

    I saw Dave W said he recommend the 94-95 gmc computer with the red and blue connectors. I found two of them for $69 each. Also I saw about the 670 Cfm throttle body. Why these two pieces?

    thanks for any help.

  2. #2
    Carb and Points!
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    I just saw my old post on here from September. I didn't know my user name and pass word so I created this new one. I read some of the old post. Someone said don't get a mailed chip.

    I am hopping to find someone here in Nashville to tune it for me. If not, I will have to do it. I don't a laptop to do any tuning.

  3. #3
    Carb and Points!
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    Any ideas?

  4. #4
    Super Moderator dave w's Avatar
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    Quote Originally Posted by Mgezee2818 View Post
    Any ideas?
    I've help several members "Tune" their chip using TunerPro RT. Here is link for additional TunerPro RT information: https://ls1tech.com/forums/lt1-lt4-m...-tutorial.html

    I think "Mail Order" chips get a bad reputation because both the vehicle owner and the"Mail Order" chip supplier are NOT up to speed with TunerPro RT!

    The second generation TBI computer 93 - 95 with red / blue connectors are nearly 50 times faster than the 92 and older first generation TBI computers with black connectors. The second generation TBI computer will have two spark tables and two fuel tables, Near Idle and Off Idle. Having two fuel and spark tables is very helpful to get a good idle and good performance for a modified TBI engine. Tuning with a Wide Band Oxygen Sensor (WBO2) is a superior method for tuning TBI, which TunerPro RT supports.

    My thread for WBO2 tuning: http://www.gearhead-efi.com/Fuel-Inj...g)-Spreadsheet

    dave w

  5. #5
    Carb and Points!
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    Dave,

    The first link, the TunerPro RT is not found. Can you resend? Okay, I will purchase the 93-95 computer with the red and blue connectors. That for the information. What's next after getting the new computer and downloading RT?

  6. #6
    Carb and Points!
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    Should I get another tbi? The 670 or a highly modified one? I read the 670 has issues such as rough idle etc. what are your thoughts?

  7. #7
    Electronic Ignition!
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    Ima thinkin it was the following link...https://ls1tech.com/forums/lt1-lt4-m...-tutorial.html

  8. #8
    Carb and Points!
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    Quote Originally Posted by stew86MCSS396 View Post
    Ima thinkin it was the following link...https://ls1tech.com/forums/lt1-lt4-m...-tutorial.html
    Got it thanks

  9. #9
    Super Moderator dave w's Avatar
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    Quote Originally Posted by Mgezee2818 View Post
    Dave,

    The first link, the TunerPro RT is not found. Can you resend? Okay, I will purchase the 93-95 computer with the red and blue connectors. That for the information. What's next after getting the new computer and downloading RT?
    Updating to a 93 - 95 2nd generation TBI computer is not a simple Plug-n-Play swap. The wiring connectors to the TBI need to be repined or build an adapter plug, see attached pics.

    For the time being the BEST PLAN going forward is to "Come Up to Speed" with TunerPro RT. After you get data logging figured out, then updating to the 2nd generation TBI computer would be a good option.

    dave w
    Attached Images Attached Images

  10. #10
    Super Moderator dave w's Avatar
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    Quote Originally Posted by Mgezee2818 View Post
    Should I get another tbi? The 670 or a highly modified one? I read the 670 has issues such as rough idle etc. what are your thoughts?
    As a general rule, performance modifications to a TBI system require some "Tuning" of the PROM Chip programming. Usually a few data logs will be required to "Tune" a 670 CFM Throttle Body.

  11. #11
    Carb and Points!
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    Quote Originally Posted by dave w View Post
    As a general rule, performance modifications to a TBI system require some "Tuning" of the PROM Chip programming. Usually a few data logs will be required to "Tune" a 670 CFM Throttle Body.
    Understood. So, what is the easiest way to do this? I really don't have time to get into all the technical things of preparing my truck to tune it. How can I simplify this? Can I take it someone locally who does this? Do you do this for a fee or do you know someone who can set me up with thingand I can have my mechanic to do it? Being in the military, I am on call a lot and can't get around to this right now. Thanks for any help.

  12. #12
    Super Moderator dave w's Avatar
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    I'm a military veteran, I completely understand the many challenges of military service. I don't think there is an easy way to tune a performance modified TBI engine. The members I've help with "Chip Tuning" were able to provide TunerPro RT data logs.

    dave w

  13. #13
    Super Moderator dave w's Avatar
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    Attached are a few screen shots of information I use from TunerPro RT to tune a chip. These pics are from a "tune in progress". The vehicle is a 1992 K1500 with a performance TPI 305, roller cam, Trick Flow Heads, Cold Air Intake, with long tube headers flowing into 2 1/4" dual exhaust.

    Knock Retard is not good.

    VE fuel is close.

    A few more TunerPro RT data logs needed.

    dave w
    Attached Images Attached Images

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