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Thread: Tuned Vortec TBI to MPFI on 7427

  1. #1
    Fuel Injected! woody80z28's Avatar
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    Tuned Vortec TBI to MPFI on 7427

    I built a Vortec TBI in 2011 and tuned it so it runs pretty well. A little bit lazier than I expected to be honest, but the BLMs are all really good and driveability is good.

    I'm taking that engine and putting it in a new truck (also a 94 with 7427) and would like to convert to MPFI at the same time. The hardware stuff is easy and I've looked at the how-to and changing the resistors on the ECM and adding a jumper on the PROM looks pretty straight-forward. My question then comes to the changes I'll need to make in the BIN. I went through the noted flags and checked/unchecked them, but the calibration stuff is where I'm stuck.

    Anyone have a clue about my used blue top Bosch/Accel/Ford 280150967 injectors? So far the Googles have failed me on finding the voltage offsets. I couldn't confirm that that are high impedence either.

    For Crank BPW vs temp, do I just change the pulse width based on the total injector math? So 2x80lb=160, and 8x36lb=288, so I multiply the current numbers by 0.55?

    I'm excited to get started on this. It's a project I've wanted to do on my current truck for years, but haven't had a chance. My new truck2.0 will have a lot of those procrastinated projects...haha
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

  2. #2
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    Quote Originally Posted by woody80z28 View Post
    I built a Vortec TBI in 2011 and tuned it so it runs pretty well. A little bit lazier than I expected to be honest, but the BLMs are all really good and driveability is good.

    I'm taking that engine and putting it in a new truck (also a 94 with 7427) and would like to convert to MPFI at the same time. The hardware stuff is easy and I've looked at the how-to and changing the resistors on the ECM and adding a jumper on the PROM looks pretty straight-forward. My question then comes to the changes I'll need to make in the BIN. I went through the noted flags and checked/unchecked them, but the calibration stuff is where I'm stuck.

    Anyone have a clue about my used blue top Bosch/Accel/Ford 280150967 injectors? So far the Googles have failed me on finding the voltage offsets. I couldn't confirm that that are high impedence either.

    For Crank BPW vs temp, do I just change the pulse width based on the total injector math? So 2x80lb=160, and 8x36lb=288, so I multiply the current numbers by 0.55?

    I'm excited to get started on this. It's a project I've wanted to do on my current truck for years, but haven't had a chance. My new truck2.0 will have a lot of those procrastinated projects...haha
    Try leaving the cranking BPW alone. Once I had mine in MPI mode it started well with minimal changes. For that matter it started and ran on a stock TBI tune suprisingly well after setting the injector size to match. 4x24=96 lb/hr.

    Most would probably laugh but I had pulled the PCM out of my G20 when it layed dormant for ~5 years. I lost the chip and file that ran it. I wanted to load it onto a trailer to bring it home. I hooked a TBI PCM to it, timing still set to 10 BTDC, put a battery into it, sprayed a shot of ether into the throttle body feeling the injectors were probably gummed up anyway, hit the key never even hearing the fuel pump run and the cammed 383 ported head Vortec TPI with SLP runners roared to life and stayed running. After a few seconds it settled down to a normal idle and after about 1 minute or so went into closed loop and ran as well as any OEM TBI 350, lol.

    https://youtu.be/VvmK__hH-Fg

    Even on 5 year old gas it still ran good.

    https://youtu.be/t5O1if1DpRo

    The videos above were running a completely stock junkyard pull 95 Van computer and a stock GM BJYN Memcal. It ran a little rich but honestly I could of driven it to and from work the way it was running and other than the annoyingly low TBI shift points it actually drove really well.
    Last edited by Fast355; 03-06-2019 at 07:32 PM.

  3. #3
    Fuel Injected! woody80z28's Avatar
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    Damn, that does sound good! haha

    This is probably the best exhaust video I have of the Vortec TBI:

    https://www.youtube.com/watch?v=dHipLkOYmL8
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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    Quote Originally Posted by woody80z28 View Post
    Damn, that does sound good! haha

    This is probably the best exhaust video I have of the Vortec TBI:

    https://www.youtube.com/watch?v=dHipLkOYmL8
    Sounds good!

    I am actually suprised it ran as well as it did on the TBI PCM. I thought it would at best limp onto the trailer. I actually did a little burnout in the street after I unloaded it off the trailer. It was parked when I lost 3 & 4th on the 3rd 4L60E that was in it.

    That exhaust setup was thorley tri y headers into dual 2.5" pipes, X pipe where the cat usually sits on those vans and dual flowmaster 40s with the OEM style dual pipes in stock location for that year van. Sitting at a redlight you would never suspect it had a cammed 383 TPI lol.
    Last edited by Fast355; 03-06-2019 at 07:47 PM.

  5. #5
    Fuel Injected! woody80z28's Avatar
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    I measured my injectors and they are 14.5ohm, so I'm good there. Would still like the know an estimated offset if anyone knows how to figure that out.

    However, that new 94 truck is a rusty POS, so I'm buying a clean 92 with the 7747. I still want to use the 7427, so I see I can either repin or I should be able to swap the harness from my current 94 donor truck. Which do you think would be easier? I'm worried about damaging pins during the repin process. I had trouble with it when I tried just one pin on my Beretta with a mini screwdriver, but this how-to makes it look easy with a homemade paper clip tool: http://www.dynamicefi.com/RePinHowTo.php

    Any other tricks to the process? I suppose I can try to repin and then swap harnesses if it goes south...
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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    Would still like the know an estimated offset if anyone knows how to figure that out.
    https://web.archive.org/web/20160305.../injectors.htm
    They are in Ford-Speak so you will need to translate. :)

    Also Ford OEM 36 here:
    http://www.efidynotuning.com/injdata.htm

    And a Ford Motorsport 36# here:
    https://injector-rehab.com/shop/lag.html

  7. #7
    Fuel Injected! woody80z28's Avatar
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    Quote Originally Posted by 1project2many View Post
    https://web.archive.org/web/20160305.../injectors.htm
    They are in Ford-Speak so you will need to translate. :)

    Also Ford OEM 36 here:
    http://www.efidynotuning.com/injdata.htm

    And a Ford Motorsport 36# here:
    https://injector-rehab.com/shop/lag.html
    Thank you thank you. As long these "Accel" injectors are actually the Ford ones that should put me in pretty good shape.

    Anyone have thoughts or tips on the repin process?

    I'm guessing the will be plenty of unused spots on the 7427 connector with no etrans in the truck.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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    I print the pinouts for both ecm's then make a quick Excel sheet. I use a format something like A1 -> B5 to indicate when a wire is removed (A1) and where it will be re-installed (B5). I include a column for handwritten notes as well because you can always run into an unexpected situation or need to take a break. There will be many unused circuits without an electronic transmission.

    Note that the Ford Motorsport injectors have different specs than the OEM version. I'm not sure which ones the Accel injectors match. We had a link or specs for various Accel injectors here. I went with the Ford number thinking you'd confirmed they were the same. Here is the data straight from Accel: https://images.holley.com/injectorofftimedata2.jpg

  9. #9
    Fuel Injected! woody80z28's Avatar
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    Well, that was more of a nightmare than it needed to be! Took 7 weeks of fighting with transport companies and some help from my bro-in-law in Reno...but it's here from Cali.


    I was a little worried the 6299 computer in it wouldn't work, but according to JeepsandGuns it should be the same as the 7747 to 7427 swap. Plan is to get it running on TBI first after the ECM swap and then do the MPFI conversion when I swap engines.

    Here's a quick & dirty photoshop of the plan for it!
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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    Everything I'm coming up with for those injectors indicates 38#/hr EV1 pintle style. 357TBI? What heads and cam? I'd think that an injector that delivers 38#/hr at 39.15psi would be too much (40.05#/hr) at 43.5psi, even for a fairly healthy 383. If it feels lazy in TBI form, probably not enough timing and maybe a little too much fuel with whatever TBI injectors you're running. For an MPFI 357 with 170/175cc heads and a cam in the 212-218 range I'd expect to need 28#/hr for 345-365FWHP. Mildly ported Vortec heads (with .550 roller springs and stud boss machining) in the 180-185cc range with a 218-226 duration range/ .525 lift cam would yield you low 400sFWHP. And that would only need about 32#/hr at 43.5psi. I'd be looking for a reconditioned set of M-9353-BB302 EV6 injectors with nozzles instead of pintles. Much better spray pattern/ atomization. If you're running too much intake runner loss of tumble/ port velocity would also contribute to a lazy feeling.

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    Fuel Injected! woody80z28's Avatar
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    Stock Vortec head, 207@.050 LT1 cam, Edelbrock Performer manifold combo. I think the biggest thing making it feel lazy was the steel wheels. Borrowed a set of aluminums once and I was amazed at the difference.

    Got the new truck running TBI on the 7427 and drove it in the garage. Was getting excited to start playing with it...and then the wife found a truck I couldn't pass up. So this one will be getting sold as-is cause I have too much other stuff to do. Kinda disappointed because it would have been cool to do this MPFI conversion finally. But I ended up getting a Vortec 8.1/ZF6 6spd 2500HD for less than this 1500 was going to cost me. So I had to think with my head, not my heart...
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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    Quote Originally Posted by woody80z28 View Post
    Stock Vortec head, 207@.050 LT1 cam, Edelbrock Performer manifold combo. I think the biggest thing making it feel lazy was the steel wheels. Borrowed a set of aluminums once and I was amazed at the difference.

    Got the new truck running TBI on the 7427 and drove it in the garage. Was getting excited to start playing with it...and then the wife found a truck I couldn't pass up. So this one will be getting sold as-is cause I have too much other stuff to do. Kinda disappointed because it would have been cool to do this MPFI conversion finally. But I ended up getting a Vortec 8.1/ZF6 6spd 2500HD for less than this 1500 was going to cost me. So I had to think with my head, not my heart...
    I had almost that same combo in my G20 Van years ago. I had a LT4 cam with 1.6 rockers. It was a tire smoker even with 3.08 gears.

    You will enjoy the 8.1. I have one in my 99 Tahoe with a 4L80E behind it. 3.42 gears and P305/50R20s on it. Even with the low-end torque loss of the Mercruiser 496 HO cam it roasts the tires if you get on it more than about 1/2 throttle in first gear. It has a healthy dose of HP Tuners editing. I have seen 17 mpg running 70 mph running in leam cruise at 16:1 air/fuel ratio.

  13. #13
    Fuel Injected! woody80z28's Avatar
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    Quote Originally Posted by Fast355 View Post
    I had almost that same combo in my G20 Van years ago. I had a LT4 cam with 1.6 rockers. It was a tire smoker even with 3.08 gears.

    You will enjoy the 8.1. I have one in my 99 Tahoe with a 4L80E behind it. 3.42 gears and P305/50R20s on it. Even with the low-end torque loss of the Mercruiser 496 HO cam it roasts the tires if you get on it more than about 1/2 throttle in first gear. It has a healthy dose of HP Tuners editing. I have seen 17 mpg running 70 mph running in leam cruise at 16:1 air/fuel ratio.
    I've been researching HPTuners vs EFILive to dive into this thing. This BlackBear place has a good reputation and they use EFILive stuff. But HPTuners is cheaper and that would save me some cash vs getting a "base" tune from BlackBear.

    What have you found the 8.1 responding well to? I would guess some more spark and less PE fuel. How do you keep lean cruise from activating while towing? My manual trans doesn't have a tow/haul button.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

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