LT1 and a T56 in a 55 Chevy

Discussion in 'Engine: Repairs , Modifications ,trouble shooting ' started by 2Loose, Jan 26, 2013.

  1. 2Loose

    2Loose reliable source of info

    Have one port on the right side open for a vent to the Optispark...

    New parts are on order for the crankcase vent system, which uses
    those two lower ports, plugged the upper ones for the time being...
    And finally learned that this top port on the plenum is for a MAP sensor...

    Pulled out all the wiring and electronic gear, and started scratching my head...

    More later....
    ( I hope !)
  2. T-Test

    T-Test Well-Known Member

    Please read the instructions/ installation material FIRST before you even unbox anything so you will KNOW what you are looking at and what it does and where it goes. I am speaking from experience and I was ASE Certified Auto Technician for over 35 years, but I am still learning, even though I don't do much work anymore.
  3. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    yes Id second that bit of advice! so many times I get called over to help in some project, only to find the problems the guys hoping I can solve could have been avoided entirely ,
    if the guy whos at this point is going partially insane, had only bothered to carefully read the details or installation instructions.

    many times youll see the guy ordered the wrong part number, and theres a very similar component that exactly matches the concept ,
    hes currently waist deep into, only to find the component he ordered is not compatible with the rest of the parts, hes working with.
    Ive seen guys order high impedance injectors that are installed on a controller designed for low impedance injectors

    You can measure the resistance across the two electrical terminals of the injector. If the resistance is between 1.5 and 4.0 Ohm you have low impedance injectors. If the resistance is between 8 and 16 Ohm you have high impedance injectors.

    Low impedance (peak and hold) injectors have a resistance of between 2 and 4 ohms. High impedance(saturated) injectors have a resistance of between 10 and 14 ohms. Low impedance and high impedance injectors cannot be used interchangeably without modification of the injector drivers.
  4. 2Loose

    2Loose reliable source of info

    You guys are exactly right on, and, oh yes, I've been there too....
    I just carefully unpacked the paperwork (instructions) from each seperate bag of wiring parts,
    and rewrote the # and name from each sheet on a fresh piece of paper, and put that in the bag,
    and have all the instructions 3 hole punched and in a loose leaf binder where I can now sit down
    and carefully study all of it. I ordered the American Autowire Classic Update kit and the
    FAST setup some ten years ago,
    and then had some quite severe health problems that made me put this project aside for quite a
    few years, but now with my health back, I'm back at it. With all the new stuff out these days, I'd
    probably be doing it quite differently, with all the new carb style efi systems out now, wow !!
    But I'm committed to using these parts I bought back then, and making them work...
    I've had some excellent help from Chad Golen (Golens Engine Works, Hudson, NH),
    ( he's done a
    lot of the early LT1 and LT4 motors, and I got the fuel injectors he recommended. I'll pull them off
    the shelf and let you guys know what it is I ended up with...

    When I did the '55 gasser I used the American Autowire kit on that one too, spent some time doing it
    right and didn't have any problems with it. So except for the FAST system, I'm basically doing the same
    thing again on this '55.

    My local Napa auto parts store had what is supposed to be
    the correct MAP for this motor....

    But it obviously needs a seal of some kind, which did not come with it...
    So the search continues...

    Pulled the new throttle body off the shelf to mount...

    And found that there is a part missing underneath, now I need to
    find out what else is needed and go find it. It did come with a
    gasket for whatever is missing...
  5. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    The throttle body was heated with engine coolant to prevent icing in Midwest and East Coast Winters.
    Most Corvette guys deleted.
    I kept the coolant hoses intact on my 87 Vette.
    Likely not needed in Hawaii.
  6. 2Loose

    2Loose reliable source of info

    An intake air warmer, ok, do not need that here in Hawaii, lowest I've seen in over 50 years was 55 deg once...
    These days, 65 min 85 max this time of year.
    I suppose I should fab a delete plate and cover it ??
  7. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Yes that will work Willy.
    Back in the day the C4 Corvette guys had Ebay sellers that sold those Coolant Bypass delete plates.
    Easy peasy job for you.
    Your a Veteran Hotrod & Fab mechanic.
  8. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    The IAC or Idle air speed control linear motor has to go somewhere Willy.
    The TPS also.
  9. T-Test

    T-Test Well-Known Member

    Are you referring to the seal for the electrical connector? If so, it should be on the wiring harness connector that plugs into the MAP sensor. Looks like a rubber accordion that goes around the oblong connector.

    Hose connects to the nipple.
  10. 2Loose

    2Loose reliable source of info

    No, looking at that opening on the MAP sensor, how to seal it...
    Here's a pic of an original '93 LT1 MAP sensor and seal,
    looks like some kind of soft sleeve...
  11. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

  12. T-Test

    T-Test Well-Known Member

    That nipple I think is where It senses the atmospheric air and had a filter on it or a hose that went to a filter. Just leave it open and see what happens. I think it will be alright. I hate electronic stuff, especially without a service/repair manual. Might find it in one of those.

    That last picture Grumpy post is of the pigtail and the seal I spoke about.
  13. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    The Map sensor detects engine vacuum levels. Or engine load.
    Used in conjunction with the LDV/8 Bin files in the ECM.
    The LT Map sensor drops in the front or rear of the intake I recall. Held down with screws or small metric bolts.
  14. 2Loose

    2Loose reliable source of info

    yup, Manifold Absolute Pressure, it needs to seal into the plenum for that signal...

    Found an old original MAP seal, but would much prefer a new one...
    Will go back and hit up my local Napa store...

    Found a piece of 1/8" aluminum plate in the scrap pile...

    Cut out a cover plate for the throttle body hot water passages,
    now I need shorter screws...
  15. Grumpy

    Grumpy The Grumpy Grease Monkey mechanical engineer. Staff Member

    read these threads and related info

    removing the coolant passage that provides hot engine coolant to heat the throttle body from the throttle body, is ok, but don,t remove the IAC sensor


    keep in mind with some aftermarket efi intakes the throttle body coolant component of the IAC throttle body housing must be removed to allow the t-stat housing to fit
  16. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

    Grumpy is Correct Willie.
    I should have went out and looked at my 87 Corvette with ITS 350 Tuned Port engine.
    Just not on the road anymore 350Tpi & LT1-LT4.
    Thinking Race Car Non stop also.
  17. 2Loose

    2Loose reliable source of info

    That nipple needs to be sealed into that hole in the plenum, I've been unable to find the correct seal for the MAP, so will probably use a good quality silicone sealer...

    Managed to find some (metric) m4 size ss allen head screws for this cover plate I made, still a little long, had to trim them slightly to get a good fit, but it came out pretty nice, also used flat and lock washers under each screw....

    More pix here (scroll down)
  18. 2Loose

    2Loose reliable source of info

    You guys have answered a lot of questions, and I need to study, study, study....

    Worked up a list of sensors needed for this
    '93 LT1 speed-density efi system a couple of days ago,
    so I'll just post it here for now, and I'm sure some of
    the answers are above:

    1. MAT
    Manifold Air Temperature
    This fits in the air ducting in front of the throttle body,
    I need to find one.

    2. ECT
    Engine Coolant Temperature
    Not sure what this looks like or where it goes.

    3. IAC
    Idle Air Control
    I think this goes on the end of the throttle shaft
    on the throttle body, I need to find one.

    4. TPS
    Throttle Position Sensor
    Again, I think this goes on the throttle body someplace,
    I need to learn more about this one.

    5. MAP
    Manifold Absolute Pressure
    Bought a new one from Napa,
    it needs a special seal that did not come with it,
    might have to just use silicone sealer.

    6. Knock Sensor
    I need to find the correct one and
    where to mount it.

    7. O2 (Oxygen) Sensor
    I have one, need to weld a bung
    on one of the header collectors for it
  19. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

  20. Maniacmechanic1

    Maniacmechanic1 solid fixture here in the forum

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