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Thread: TPI conversion 95 GMC truck

  1. #1
    Carb and Points!
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    TPI conversion 95 GMC truck

    Hi all.

    New to EFI tuning and wanting to learn as much as I can before I dive in.
    Right now, we're building a new (to us) shop truck from several parts we have underfoot.

    The truck is a 100% stock 1995 GMC 1500.
    305 TBI, 4L60e, 3:42 gearing.
    It runs well, the stock harness is nice, and it has no codes showing.
    It runs the 16197427 PCM.

    We're not wanting to deal with the "one year only" '95 4L60e, and the 305 is getting re-purposed into another truck.

    Here's what we're dropping in.

    A non-electronic 4L60 with a recent (18K mile) HD rebuild from a reputable shop.
    Low mile (60K-ish) 350 TBI non-roller shortblock.
    Long tube headers and a 2 1/4" true dual exhaust. (no cats)

    Right now, cam, heads, induction, and ECM choices are up in the air.

    I'm favoring re-pinning to the '730 ECM, and removing the 4L60e trans wiring from the harness.
    I believe both the '730 and the '7427 have ESC filters on board the MEMCAL, so no worries about external ESC modules.
    (hopefully...)
    I know the ESC filter, KS, and cu. in. displacement all have to match.
    As I understand it, the '730 also supports on/off (not PWM) converter lockup for the 4L60. Yes?
    I will most likely have to incorporate the OEM 4L60 trans wiring/plug into the existing '95 harness. No problem.

    I'm not sure if there's any difference in the VSS signal between the '95 4L60e and an earlier ('89) 4L60, or between the '7427 and the '730 ECM?
    Optical-vs-magnetic?

    As far as cam choice, we've pretty much settled on the old Mellings MTC-1 grind, or the Summit #K1102 equivalent.
    (204*/214* @ .050, .421/.444 lift, 112 LCA)
    This truck will serve as my wife's back-up vehicle, our shop truck, gopher, daily, winter beater, etc. do-all pickup.
    (no towing)
    It has to be relatively mild mannered and fairly fuel efficient.

    For induction, I'm really wanting to pull an old TPI off the shelf I've had for 20 years collecting dust.
    It's an '87 unit off of a 305 Camaro. Just the hardware, no harness, or ECM with it.
    It will of course, be ran as a SD setup with the '730 ECM.

    Heads with the TPI are pretty much limited to what we have on hand. Stock #193 swirl-port truck, with 64cc.
    (unless a nice pair of '083 heads find their way to my front porch....)

    Option #2 is a fresh pair of L31 Vortecs that are on the shelf, and either an aftermarket 4 bbl. Vortec intake with single or twin TBI's, or....

    May try running a stock Vortec MPFI (not CSFI) in batch-fire mode?? Anyone tried that?

    Most likely a pair of .015 steel shims will find their way under whatever heads we go with, and dual electric fans are in the plans. Does the '730 ECM support electric fans? One? Two?

    Tuning is going to be handled by either Moates APU1 Autoprom, or Dynamic-efi. Still undecided....

    It's going to be a low-budget build, so it's more of a learning experience than anything else.
    Most of the cash saved, and experience gathered on this one, will be put to use on my other "toy", later.
    ('93 Gen V 454 with a vintage SuperRam MPFI)

    I know the '95 trucks are kind of an oddball, so any help or suggestions would be greatly appreciated.

    TIA.

  2. #2
    Super Moderator dave w's Avatar
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    I'm confused, why use the '7730 when there is an easier and less expensive option to use the '7427 in MPFI mode?

    See attached .zip for details.

    dave w
    Attached Files Attached Files

  3. #3
    Carb and Points!
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    Hi Dave.
    Thanks for the reply.

    Basically, I figured swapping to the '730 would give me the option to tune with Dynamic-efi.
    I didn't see any support for the '7427 on their site.
    Also wanted 4L60 compatibility, and the '7427 used in the '95 trucks is sort of an oddball from what I've gathered.
    PWM converter lockup and shift solenoids with one year only Ohm specs.

    I didn't know if that was all in the programming, or built into the PCM itself.

    Can I run a '7427 with a 4L60? Like a '95 MT program?
    How do I handle TCC lockup?

    Mike

  4. #4
    Super Moderator dave w's Avatar
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    There are numerous options.
    Using the Moates.net Ostrich 2.0 chip emulator ( http://www.moates.net/ostrich-20-the...eed-p-169.html ) with a '7427 is "On Par" with the Dynamic EFI system. Both the Ostrich 2.0 and Dynamic EFI system use TunerPro RT to upload / download a "Tune File".

    Possibly installing PWM delete kit ( https://gmtnation.com/forums/threads...from-tcc.7238/ ) into the 95 4L60E is an option, so the '7427 can use a "Tune File" from a 1994 '7427 non-PWM 4L60E.

    I've done several '7427 MPFI conversions, it's an AWESOME low cost option!

    dave w

  5. #5
    Super Moderator dave w's Avatar
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    Pic of a 16197427 connected to an Ostrich 2.0.

    dave w

    DSCN4240.jpg

  6. #6
    Carb and Points!
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    Thanks for the link.
    I had no idea TransGo offered a PWM eliminator kit. PWM on a clutch apply circuit never made any sense to me. Just more/faster wear.
    That would be a nice upgrade to the '96-newer 4L60e's.

    I pretty much need to run the 4L60, though.
    One, I have it in front of me, and I know the history on it. Two, the '95 4L60e is in a 2WD configuration, and the truck will end up equipped with 4WD when it's done.

    Essentially, what we have under our current shop truck is a well maintained 4WD chassis with upgrades we'd like to keep, but the sheetmetal is toast.
    The '95 is a cleaner truck, so it's getting a chassis conversion. the 4L60 comes with the chassis, along with a recent Moog front suspension and a 14 bolt SF rear with a locker. Wheels, tires, brakes, etc. Just too fresh and reliable to abandon.

    The two combined will make a respectable shop truck, and a TPI should add a little fun to the mix.

    Mike

  7. #7
    Super Moderator dave w's Avatar
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    The 16197427 has programming for TCC only, so using either a 700R4 or 4L60 are options with a 16197427.

    The 16197427 usually requires a VSS, 2000 pulses per mile or 2K VSS.

    dave w

  8. #8
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    It does seem a bit backward to repin for 7730 when 7427 can do the job but I understand KISS in configuration. I have repinned a 7747 truck to 7730 but I think I'd probably build a conversion harness or adapter for this one. I'd leave the trans wiring just in case, just don't connect it to the adapter. 4L60E is much easier to work with than 700R4. When is 4WD install happening? VSS output for 4L60 will come from transfer case after conversion.

    I would stay away from 4bbl plus dual TBI for work / shop truck. It's a little work to account for rapid temperature changes in manifold air and resulting fuel puddling when you have dual throttle plates. Tuned port engines were some of the best truck engines never installed in trucks. Pick a gear / tire size to keep engine rpm low and install cam that makes big torque and peak power by 4k rpm and it will run like a BBC.

  9. #9
    Carb and Points!
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    Hi, 1project2many.

    I've kind of gathered that the 7427 is the last best OBD1 PCM to use for MPFI. From what I've read, it has functions that even some of the best tuners have yet to uncover. At least that was true a few years back, anyway.

    I don't speak "tuner" very well, but my takeaway was, the 7427 does provide a lot more latitude when building a custom tune.
    I think I remember reading where it allows isolation of fuel and spark without one automatically influencing the other.
    That sounds like a benefit to me.
    Lean cruise is something that would interest me also, although I believe it's available with some other PCMs, too.

    The move back to the 7730 was my idea to, like you say, K.I.S.S. I know that was GM's answer for SD TPI, and Dynamic-efi offers it already modified.

    I know the 7427 would be my first choice when it comes to the 454/4L80e MPFI build, but the shop truck, in my mind, was going to be "bare bones" simple and relatively easy with the 7730. (but again, I'm a newbie. LOL)

    4WD will be the final stage of the build.
    Right now, the plan is to assemble the 350, drop it in the '95 with the OEM TBI setup and break the cam in.
    We have a spare 2WD 4L60 to mock it up and run it with.
    Once we're satisfied everything is good to go, we'll put a few miles on it, evaluate it, and then swap on the TPI and start sorting the wiring out.
    (think of it as a mobile test bench)

    There's a little paint and trim stuff to do, then we'll blow the current truck apart and roll the 4WD chassis under it some weekend.
    These trucks are remarkably easy to work on...

    I like the idea of tucking the e-trans harness away, just in case I happen to stray across a 4WD 4L60e at a later date.

    Quick question. Will the 7427 support ALL GM automatics? 4L60, 4L60e (all years), 4L80e.
    Say I happen to find a nice 93-94 4L60e. Am I good with using it?
    I know it depends on the bin. but I just don't recall this ECM being used with a '60e and on/off TCC. (93-94)

    I'm glad Dave brought up the VSS pulse info. (Thanks, Dave)
    Up till now, I've dealt mostly with the 88-94 trucks that had the DRAC from 92-94.
    They used a 4K VSS pulse that split to the ECM (I think) and 2K to the speedo, RWAL brakes, and the cruise control module.
    This '95 doesn't have a separate DRAC module does it? Didn't see one...

    May be another reason to stay with the 7427 if the DRAC function is now handled by the PCM on '95s?

    (You guys are slowly talking me into it...Hahaha!)


    The twin TBI idea has always interested me since TurboCity offered one way back when. (briefly)
    Just a novelty thing, mostly.
    That was option #2 if I went with the Vortec heads and intake. Figured a pair of 2.8 V6 TBIs would yield around 670 cfm.
    Injectors, I'd have to see what math'd out best.
    Just had to figure out how to fab a nice top plate for the Vortec lower plenum. Something on the order of the old Vette Crossfire setup, only inline.
    I'm sure twins would present their own set of problems, though.

    I think for now, the TPI on the truck heads should work fine for a shop truck.

  10. #10
    Super Moderator dave w's Avatar
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    The 1995 Pickup will have a VSSB / DRAC.

    The 1995 VSSB / DRAC sends 2K VSS pulses to the 16197427.

    The 1227730 / 1227727 uses a 4K VSS.

    dave w

  11. #11
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    '730 / '727 can be made to take the 2K VSS pulse with a flip of a bit. Have it written down in my notes but doesn't do me any good since I can't find them!

  12. #12
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    I did the tpi conversion on a 95 with the help of fast355, dave, haulina$$, and a few others. I wrote up just about everything at:
    https://www.gmt400.com/threads/tbi-t...on-mpfi.39486/
    Other than an oil leak ill track down when i get motivated it runs great. Its not something I wanted to do for an increase in power (which there probably is none) but I had my camaro sitting next to the truck and thought a TPI in the truck might make an interesting project
    Last edited by pro; 01-20-2019 at 02:16 AM.

    1992 Camaro Z28 5.7
    1995 Silverado 5.7 TPI

  13. #13
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    '730 / '727 can be made to take the 2K VSS pulse with a flip of a bit. Have it written down in my notes but doesn't do me any good since I can't find them!
    Sounds like the optical / magnetic VSS bit? Optical sensor produces 2k square wave 0-5V. Easy solution if you have the right signal.

    Not quite tuned port, but this 89 GMC was switched to 7730 and PFI after the 7747 just didn't allow the flexibility the owner wanted. If the truck had been 4L60E equipped I would have opted for a 7427.











  14. #14
    Carb and Points!
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    Gaining more good info. Thanks for the replies, guys.

    That's a nice looking install,1p2m. Mercruiser Magnum?

    I had looked and looked for a 502 Magnum EFI takeoff for my 7.4L, but finally settled on what I think, is an early Street & Performance Super Ram.
    I'm not sure what manifold S&P used, but when the whole truck came up cheap, cheap on Craigslist under "Parts", I grabbed it.
    Supposedly, it was installed sometime in the mid '90's on a '92 Suburban.
    Evidently, it ran well for almost 200K and finally gave up the ghost in summer '18. (head gasket)
    It's mine now....

    I think Dave has convinced me to stay with the 7427, as there are things particular to the '95 crossover truck that makes that a better decision.
    Also, considering the 4L60e's neutral safety switch and reverse light setup, the existing trans. harness, and shift point tuning, all things point to rounding up a known good 4WD 4L60e for this build.
    In the past, I've swapped selector shafts and built custom brackets to retain the P/N/reverse light switch, but that's just more unnecessary work for no real gain.
    Just hate to shelve my good 4L60 when it performs so well....lol!

    I put a few calls out today for a good '93-'94 4WD 4L60e. I'll see what comes up.
    Meanwhile, I'm going to kick back and peruse pro's link over at gmt400. (Thanks, pro!)


    Mike

  15. #15
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    you will be happier with the 4l60e and its key stroke tunability rather than having to drop the valve body or governor to make. shift point changes. you may want look for a 4l80e and "be done with it".

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