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Thread: Which TBI system is better?

  1. #31
    Super Moderator Six_Shooter's Avatar
    Join Date
    Feb 2011
    Quote Originally Posted by fastacton View Post
    I'm not an expert on it, but I believe that the force motor operates at a different frequency and has a cleaning cycle that the '7427 doesn't support. I've heard of people using the early trans with the '7427, but not sure how long they'll last like that.
    I talked with a friend of mine who is a 4L80E nut, I mean a real 4L80E nut, not just someone who likes them. So far his car (1971 Cutlass), his girlfriend's car (1988 Chevy Caprice) have 4L80Es installed, and his 1992 (I think) Old Custom Cruiser is getting a 4L80E as well, all behind Olds engines. lol

    Anyway, after looking up some reference material he has it indicated that some cars had the force motor valve algorithm to keep the valve from getting stuck, however it only does this in park and it sounds like many domestically sold vehicles didn't have this enabled. Later PCMs don't seem to have this and those transmissions seem to be fine. The change in frequency also doesn't seem to be a problem from his experience.
    The man who says something is impossible, is usually interrupted by the man doing it.

  2. #32
    Super Moderator Six_Shooter's Avatar
    Join Date
    Feb 2011
    Quote Originally Posted by KeyAir View Post
    Ok, things just changed up.
    I have to have the Motorhome up and running in 2 weeks to move it.
    Put the Quadrajet on and its just not running right.

    Can I do the basic TBI conversion using the '87 stuff in that time frame?
    I need a running vehicle, not smog compliant in 2 weeks.

    Tomorrow I can go get the box that I stashed the '87 Throttle body/wires/ecu etc.
    The '90 harness I have may be more complete, so maybe I should use that as the ECU is the same...

    Not worried about smog pump and cats yet, unless they are needed to run the engine.
    I will need to pull the LH banks header to install the O2 bung.

    I've done EFI conversions in a weekend, so it's possible, but if you're less experienced in conversions it may not be so easy, or you may need to dedicate more time to it than you actually can spare over the next two weeks.

    That being said you don't need any of the emissions control components in place for the engine to run. Going TBI, it makes the swap to be a little more than a carb swap. Swap the carb for the TBI, the dizzy for an EFI one and add a couple more sensors. You will also need to add the fuel pump and the wiring.

    If you take a couple hours to lay all the parts out and plan the swap you should be able to come up with a plan to get everything working, even if you will need to go back in later to re-work the harness to pretty it all up.
    The man who says something is impossible, is usually interrupted by the man doing it.

  3. #33
    Fuel Injected! 1BadAction's Avatar
    Join Date
    Apr 2012
    Dallas, TX
    I have nearly 15 thousand miles running a 7427 on a 4l80E manufactured in 1990 (1991 model year) without a single issue, and thats on top of 78,000+ miles the trans ran on a 7060. I had to tune the force motor current tables to get the pressure in line with what was commanded but it didn't take much. If I had it to do over I would have thrown the 7060 in the trash from the start.
    2010 Porsche Cayenne GTS - DD
    1991 2500 Suburban - 454ci BBC tow monster
    1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac

  4. #34
    Fuel Injected!
    Join Date
    May 2011
    Pocono's PA.
    Quote Originally Posted by 1BadAction View Post
    If I had it to do over I would have thrown the 7060 in the trash from the start.
    Pretty much sums it up .......

    Oh , and I have ran late ('96) '80E's with the 7060 and early ('91) '80E's with the 7427 with no problems either way , I am sure there are differences , but I digress to think they are that big of a deal . My trans guy says no , but some say yes , Dunno.......

    Last edited by Nasty-Z; 12-02-2015 at 11:51 AM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  5. #35
    Fuel Injected!
    Join Date
    Aug 2012
    That good 80e info. My main truck is a 94 and a 6395/7427 but have a 93 trans that came with 7060 and it is destined for my 50 pickup with a 7427.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  6. #36
    Fuel Injected!
    Join Date
    Nov 2013
    Green Acres
    I can offer all of you advise with the 4L80-E. I did this for a living many years within GM Calibration. My personal old 77 crew cab I converted to a 4L80-E with only off the shelf parts with the 94-02 TCM from the 6.5L diesel stand alone. (Later adding EFI but kept the TCM)
    I observed within and outside shops to find what shops are using to "Fix" the units. I read some use a 91-93 Bosch Force Motor unit and control it with the 94 forward PCM. I wouldn't run this high risk combo on my own truck. I don't think even the best trans shop could actually find the root cause of failure without the knowledge. If you start with some basic paired parts you will have better service and prevent future overhauls.
    Some kits have you drill holes in the pump to combine two circuits and one has you "open" a bleed for the pressure reg. balance. These will only lead to noise and unstable line pressure. Another fix causes the converter cl to drag worse increasing the wear factor. This leads to TCC Slipping and Trans Component Slipping codes. The thoughts behind these fixes are not well and completely thought out. They were to address failure modes that were not completely understood. I've fixed many. Sadly these shops believe they do correct the problem when they didn't diag it right.
    If you can "Tune the Force motor tables" in a short period of time, the personal who do this take over two weeks to get this correct. My offer is proven with knowledge gained from many years. It's your vehicle and your back to pull it out. If someone says these mix of 91-93 4L80-E with a 94 forward PCM is ok, it's only a matter of time before it fails in my opinion.
    If one takes a 91-93 Bosch FM unit/Valvebody assem and installs a Holley or Borg-Warner force motor in this VB, I suggest you take the time to investigate this. Get the manuals and lay the hydraulic circuits beside each other. You should see why.
    I don't know it all and never will. I can only offer lessons and the knowledge behind this that may provide many miles of trouble free use. From combos to cooling to mixing parts.
    Last edited by billygraves; 12-02-2015 at 04:50 PM.

  7. #37
    Electronic Ignition!
    Join Date
    Nov 2014
    Thanks for the AWESOME input guys!

    My nightmare before Christmas has kept me busy!

    The move ended up happening with just the carb in place, as I had a bunch of issues to resolve before i could even get it done.
    Could not get the engine to run well enough...
    Added a Innovate Fuel/Air meter, which pointed me toward a seriously rich condition.

    Here is my Banks header, off and ready for the O2 bung.

    Excuse my feeble TIG attempt... still learning!

    Gauge in place temporarily..

    I found out I had set the float level too high, which was causing it to run like crap.
    Then I found the mech fuel pump had gone bad... and also found some soft weeping rubber lines.
    Ended up wrestling out the 80 gallon fuel tank to clean it, and replaced every single rubber fuel line.. some were very ugly!


    Then I found a bad leak in the PS pump, which had to be replaced, as the Airstream has Hydroboost!

    Then I found this nice toasty starter feed wire caused by a missing starter heat shield behind the hot banks headers...
    Weeping fuel lines and a nice electrical short... perfect combo!

    Added a Mr Gasket heatshield.

    Fixed all that, and it ran "OK" to move it the 50 miles!
    The plan to add the TBI is moving forward.
    Last edited by KeyAir; 01-12-2016 at 12:36 PM.

  8. #38
    Electronic Ignition!
    Join Date
    Nov 2014

    Having now added a Innovate wideband O2 sensor...
    Is there a way to get that to "talk" to the GM ECM correctly?
    Or should I just plan to add a narrowband to the other header?

    Also, a question about fuel feed..
    I am thinking about using a "Surge tank" system.
    This would mean keeping the Holley low Pressure Pump next to the gas tank(30' less wire to run), feeding into the surge tank.
    Then an inline HP pump to feed the TBI unit.
    All HP line forward of the surge tank, and low pressure rearward.

    Anyone done that or have input?

    Your input is interesting!
    I have a question for you...
    In an earlier post someone mentioned "finding a MotorHome tune" for the ECM.
    As a Noob here, I want to try to understand what that means..
    If I have this correct, the ECM number just ID's the chipset... and the letters after it ID the fuel/ignition trim that is programmed in?
    Last edited by KeyAir; 01-12-2016 at 12:41 PM.

  9. #39
    Fuel Injected!
    Join Date
    Oct 2013
    The surge tank isn't a bad idea. You can get 1/2 gallon tanks on Ebay for around $50. I guess a downside is that you have 2 fuel pumps that could fail.

  10. #40
    Electronic Ignition!
    Join Date
    Nov 2014
    Agreed, that its a solution, but of course there is 2 possible pumps to fail.
    The good news is that both are exterior pumps, so no dropping tanks to fix.

  11. #41
    Electronic Ignition!
    Join Date
    Nov 2014
    Still working on this.
    I went with a Carb setup, but I'm battling mixture issues.
    I have begun to build out/restore the TBI in preparation.

    One question I have is I cannot find the seals that are on the ends of the throttle shafts.
    Anyone have a source?

  12. #42
    Fuel Injected! PlayingWithTBI's Avatar
    Join Date
    Dec 2018
    Quote Originally Posted by KeyAir View Post
    One question I have is I cannot find the seals that are on the ends of the throttle shafts.
    Anyone have a source?
    Try this guy, he should be able to help you.

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