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Thread: 1990 7.4L Rock Crawler Tuning

  1. #1
    Carb and Points! Seven4Auzzy's Avatar
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    1990 7.4L Rock Crawler Tuning

    First off wanna say hi! New to the forum but I've been ghosting it for a while now so decided to join officially! Seems to have a bunch of great info and support!

    So back groundon my motor, it's from a 1990 c3500 with roughly 70k when it got wrecked back in 01. I got it in 2016, opened it up and was shocked by how well it looked inside. Cleaned it out, honed the cylinders, new rings, new gaskets and seals in and out, new sensors etc etc etc and it runs fine and doesn't leak or burn anything! Only issue im having is just the general lack of power and rpm from am earlier tbi motor and that it gets hot while running/bajaing. Like upwards of 240*.

    Current motor mods:

    -MSD coil, distributor, ac Delco ignition module, and Taylor wires with ngk plugs.
    -Custom headers with 1.75 primaries.
    -2.5 mendrel bent exhaust off the headers to a single FM 40 with a 3" tail pipe
    -All new AC Delco sensors with a 3 wire O2 Sensor
    -Summit high flow water pump and 190* thermostat
    -8rib belt system with a 10% reduction pulleys
    -Taylor throttle body spacer
    -AC Delco injectors
    -Injector body spacer
    -14psi regulator spring
    -Ls1wiringharness.com stand alone harness
    -8747 ECM


    So big thing for my rock crawler are some modifications I have planned for it, That list is as follows:

    -Switch out heads for a set of 781 or 049 heads that are going to be decked, gasket matched etc.
    -Switch out the cam for a Comp Cams 11-302-4. 212/218 duration etc
    -1.7 roller rockers since I don't think the cam is all that aggressive to need 1.6s
    -Jegs adjustable fuel pressure regulator
    -Edelbrock performance intake like a mid rise style
    -And my own tbi adapter plate

    I feel this would really open up the old beast and maybe help with the heat too with itt not being so restricted.

    My main issue with all this is that I am not that tech savvy. I've done diesel stuff, custom programming for deletes and other mods. Even used up-rev to delete my titan and modify it. So my main question is what is everyone's preferred program/connector cable/ECM/ECM mods/and chip builder??

    IMG_20190727_194629.jpg
    IMG_20190511_190228.jpg

  2. #2
    Super Moderator dave w's Avatar
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    Many options for tuning hardware, have you looked at Moates.net? http://www.moates.net/gm-19851995-c-64.html

    Most geardhead-efi members use TunerPro RT software for tuning OBD1. http://tunerpro.net/

    Gearhead-efi link to 1228747 information, including TunerPro RT .xdf / .adx / .bin files. http://www.gearhead-efi.com/Fuel-Inj...Information-4F

    dave w

  3. #3
    Carb and Points! Seven4Auzzy's Avatar
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    So if I'm understanding it I will need the moates system to physically connect it then the tunerpro for the software?

  4. #4
    Super Moderator dave w's Avatar
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    The 1228747 ECM is not "Flashed" like OBD2 computers.

    The 1228747 ECM uses a 2732 chip. There are several variants of the 2732 chip with different programming voltages, 12v, 21v and 25v. Most 2732 chips are re-programmable, but require an ultra-violet light to erase the chip before re-programming.

    Some gearhead-efi members convert the 1228747 to use a 27SF512 "Flash" chip. I posted a thread on converting a TBI ECM to a flash chip: http://www.gearhead-efi.com/Fuel-Inj...sion-(27SF512) The 27SF512 is an EEPROM (Electronically Erasable Program Read Only Memory). Electronically Erasable means the ultraviolet light is not needed to erase the chip before re-programming.

    The real "Heart Beat" for tuning is the ability to re-program the chip for things like Fuel Table Corrections and Spark Table Corrections.

    Moates.net offers affordable hardware to program the 27SF512 chip.

    dave w

  5. #5
    Carb and Points! Seven4Auzzy's Avatar
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    Quote Originally Posted by dave w View Post
    The 1228747 ECM is not "Flashed" like OBD2 computers.

    The 1228747 ECM uses a 2732 chip. There are several variants of the 2732 chip with different programming voltages, 12v, 21v and 25v. Most 2732 chips are re-programmable, but require an ultra-violet light to erase the chip before re-programming.

    Some gearhead-efi members convert the 1228747 to use a 27SF512 "Flash" chip. I posted a thread on converting a TBI ECM to a flash chip: http://www.gearhead-efi.com/Fuel-Inj...sion-(27SF512) The 27SF512 is an EEPROM (Electronically Erasable Program Read Only Memory). Electronically Erasable means the ultraviolet light is not needed to erase the chip before re-programming.

    The real "Heart Beat" for tuning is the ability to re-program the chip for things like Fuel Table Corrections and Spark Table Corrections.

    Moates.net offers affordable hardware to program the 27SF512 chip.

    dave w
    Sweet thank you!

    From what I've been reading it seems I'm gonna need to do more than just some different heads. I've been reading on the heads and other things to do with these motors and from the looks of it I'd have to swap out pistons too if I switch heads.

    http://www.minuit10.net/EngineCode/c...linderHead.htm

    According to this page my motor is a super small combustion chamber which I knew it was but not that small so stepping up to the 781 or 049 heads would require some slightly taller pistons if I'm thinking correctly

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