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

    Fitting together the fuel and exhaust systems

    Had to pull off this right side header to get a drill in
    for the last two fuel line mounts....
    [​IMG]
    The header is going to be close...
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    Yes, I'm going to need some insulation for those fuel lines
    to protect them from the exhaust heat
    [​IMG]
    Or, wrap the exhaust system to keep the heat away from the fuel lines...

    More Later....
     
  2. 2Loose

    2Loose reliable source of info

    I need to learn about how this efi system works....
    Think: '93 Camaro Z28, LT1 system, stick shift....
    What are these ports on the rear of the plenum for?
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    Also on the left side....
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    And on the right side....
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    More Later....
     
  3. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

  4. 2Loose

    2Loose reliable source of info

    Thanks,,,,
     
  5. mathd

    mathd solid fixture here in the forum

    First picture on the left(with a triangle gasket mark) is for the EGR valve.
     
  6. 2Loose

    2Loose reliable source of info

    Decided to block off the EGR (Exhaust Gas Recirculation) Ports...
    A ball peen hammer and sharp edges make cutting templates easy....
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    Gotta transfer that to some 1/8" plate....
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    Get the holes drilled accurately first....
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    And finish shaping them to fit the templates....
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    Paint next....
     
  7. 2Loose

    2Loose reliable source of info

    [​IMG]

    Trying to figure out how to connect these fuel lines on the fuel rails....
    The rear tube is 3/8" and I'm told is the fuel in connection...
    The front tube is 5/16" and I'm told is the fuel return line...
    I've ordered an AN-8 connector for the 3/8" line,
    and an AN-6 connector for the 5/16" line.

    And a tee with both AN-6 and AN-8 connections for the fuel
    return connections at the fuel PR valve...
    [​IMG]

    The upper tube in this pic is the 5/16" fuel return line.
    Under the fuel rail it is connected to that black device....
    I'm guessing that device connects to engine vacuum??
    This one is pretty old and gnarly, think I need to get a new one...
    [​IMG]

    Any Comments?

    More Later....
     
  8. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

  9. 2Loose

    2Loose reliable source of info

    Thanks for all the info, that helps a lot....

    It's been rainy here, humid, it took these block off plates for the EGR openings in the plenum forever to stop being "sticky" so I could install them...
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    More pix of this fuel return setup at the fuel rail....
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    I'm trying to find info on exactly what this device is, it looks like a manifold vacuum
    operated device to control fuel pressure in the fuel rails....
    [​IMG]

    It's obviously not adjustable, and I'm trying to find out how it operates,
    and what the specific parameters are, and if I can just dump it and
    plug the hole in the rail? Or find another one that is adjustable so
    I can tune it to my particular requirements?
    After all my fuel pressure regulator is a constant flow return type, and is mounted right next to the motor, and feeds directly into those fuel rails, so I am trying to figure out just what this device does in addition to my PR, like maybe it adds additional pressure when the manifold vacuum drops??
    Hmmmmm.....
    [​IMG]

    These are the fittings I found to attach AN hoses to these fuel lines at the fuel rails....
    [​IMG]

    More Later....
     
  10. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    #3 in the diagram, its your OEM fuel pressure regulator the vacuum line changes the effective fuel flow and pressure slightly to compensate for the engine loads
    manifold vacuum changes under engine load
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    [​IMG]
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    http://static.summitracing.com/global/images/instructions/hly-199r10036-1.pdf
    swapping to an adjustable versions usually good for a couple extra ft lbs of torque
     
    Last edited: Feb 7, 2018
  11. 2Loose

    2Loose reliable source of info

    [​IMG]
    I would think this Aeromotive fuel PR valve mounted right next to the motor would provice all the fuel control I need, and I think I can remove the stock, non-adjustable unit on those '93 fuel rails, and eliminate the fuel return directly from the fuel rails, but I am only guessing!

    Aeromotive also suggests running two inlets to the fuel rails from a tee, and at the other end of the fuel rails, combine the outlets into the Aeromotive PR and then return to the fuel tank. That seems excessive to me for this particular application, the most likely setup from what I can see now, is to eliminate that stock unit on the fuel rail, plug that hole, and feed the fuel rails inlet directly from the Aeromotive PR unit.

    The Aeromotive unit has a vacuum tap available, but I'm thinking I probably won't need to use it. Leave it at atmospheric sensing. But I can hook it up and see what it does also, it might really be a useful option.
     
  12. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    THINK,
    EFI works at higher pressures (a 1985-1991 TPI corvette as an example generally operates in the 38psi-42 psi fuel pressure range)
    THINK,

    fuel tank...to .fuel filter....to .-fuel pump....to feed into fuel rail& injectors. then out too....fuel pressure regulator...then too..return line to fuel tank




    [​IMG]

    [​IMG]
    [​IMG]

    the vacuum line to the plenum drops under full throttle,
    so the diaphragm and check ball,compensate, to maintain max flow rate to the injectors,
    the diaphragm and check ball in the regulator become, or are just a tiny bit harder for the fuel pressure too force open,without the plenum vacuum above the the diaphragm and check ball
    thus maintaining fuel rail volume and pressure before any of the fuel can exit the return line


    [​IMG]
    [​IMG]
    [​IMG]

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    it might help if you think, fuel pump provides fuel flow volume,
    fuel pressure is a measure of resistance to fuel flow,
    the fuel pressure regulator acts as a valve that opens if the pressure exceeds about 42 psi (YES some versions like yours are manually adjustable) but the reason its there is to maintain a consistent 39 psi-42 psi to do that you allow the fuel pump to stack or pressurize fuel in the fuel rail and in theory the fuel pressure regulator only allows excess fuel volume to flow back to the fuel tank through the return line if that fuel pressure exceeds the 42 psi, the pump is designed to provide a bit more than the required 42 psi too insure fresh cool fuel is cooling the fuel pump while maintaining that consistent fuel volume at the fuel pressure, when you tromp on the throttle the flow of fuel drastically increases, the regulator momentarily restricts out going fuel to maintain the fuel rail pressure and volume, until the flow demand drops enough, for excess volume and the resulting increased pressure that results to open the regulator again,

     
    Last edited: Feb 8, 2018
  13. 2Loose

    2Loose reliable source of info

    A better pic of that Aeromotive fuel pressure regulator....
    [​IMG]
     
  14. 2Loose

    2Loose reliable source of info

    I'm assuming the vacuum connection on that return line regulator allows the regulator to add a little more furl pressure in the fuel rail when the accelerator opens suddenly and the vacuum in the plenum drops, offsetting a possible lean situation.
     
  15. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    yes thats correct the vacuum line to the plenum drops under full throttle,
    so the diaphragm and check ball,compensate, to maintain max flow rate to the injectors,
    the diaphragm and check ball in the regulator become, or are just a tiny bit harder for the fuel pressure too force open,without the plenum vacuum above the the diaphragm and check ball
    thus maintaining fuel rail volume and pressure before any of the fuel can exit the return line
     

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