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Alaska; 86’ GMC Sierra Classic 1500 4x4 swb

Discussion in 'Tech Discussion' started by BJedi76, Nov 9, 2019.

  1. BJedi76

    BJedi76 Junior Member

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    Location:
    Soldotna, Alaska
    First Name:
    B.J.
    Truck Year:
    1986
    Truck Model:
    GMC Sierra Classic 1500 4x4 SWB
    Engine Size:
    350”sb
    I have an ‘86 GMC Sierra Classic 1500, 4x4 swb. w/a 700r4 trans.

    I don’t want a hot rod. I just want a smooth throttle & decent gas mileage.

    The engine is an 80’ Canadian 350” out of a California 1ton van.

    Carburetor is a 17066559 (M4MC I think)

    I live at sea level, in Alaska, where the temperature ranges from 70° in the summer to -25° in the winter.

    I am looking for a “heat stove & hot air intake air cleaner housing system.

    ...but my questions are:
    - Do i need to tune it any different in winter vs summer?
    - what rebuild parts (like jets etc) are appropriate for my drivetrain?
    - Am i on the right track or is there a different way to go?

    thanx...
     
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  2. Shorty81

    Shorty81 Baby Boomer

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    Location:
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    First Name:
    Darren
    Truck Year:
    86
    Truck Model:
    K20
    Engine Size:
    496
    Welcome from thousands of miles to the East.
     
  3. Turbo4whl

    Turbo4whl Junior Member

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    First Name:
    Wayne
    Truck Year:
    1974
    Truck Model:
    Jimmy
    Engine Size:
    350
    With all the original vacuum lines, thermal switches, heat stove, electric choke etc. installed, the engine should start and run fine at any temperature. Any parts that are missing or disconnected will effect cold start and or normal running temp.

    That engine, I believe like my '82, has trapped vacuum spark for cold starts. Very important. Also would have locking converter defeat when cold. This also helps during engine warm up. The original carb was jetted very lean for fuel economy and emissions. A richer set of jets or other fuel mods will help for cold starts, but, fuel economy and emissions will suffer.

    Do you still have a readable vacuum diagram sticker? The correct year factory service manual will have the diagram. The other question, is the carburetor the original '86, or is it from the 1980 donor?
     
  4. 75gmck25

    75gmck25 Full Access Member

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    Truck Year:
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    Engine Size:
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    The heat stove and hot air intake connects the round port on the bottom of the air cleaner snorkel to a housing on the passenger side exhaust manifold. The housing on the manifold is just two pieces of shaped sheet metal riveted on, with a round hole in the top. There is a 2" metal hose that connects this heat stove to the port on the air cleaner snorkel.

    In the air cleaner there is a temperature valve and it would be connected to engine vacuum and to the mechanism for a flapper that covers the port on the bottom of the air cleaner. When the engine starts there will be vacuum to the temp valve, which will pass through the vacuum and pull the flapper open (it is inside the snorkel and pivots up) so that hot air is drawn through the 2" pipe coming from the exhaust manifold. You are then drawing warmer air into the carburetor. As the engine temp increases the temp valve will cut off vacuum flow to the flapper and it will gradually move the flap down and start drawing air from the main snorkel.

    Getting that hot air stove mechanism working should help cold weather operation, but working on the carburetor choke will probably be more effective. The round black cover on your choke should have index marks on the top and you loosen the 3 screws and rotate it left or right to lean or richen the choke.

    Bruce
     
  5. BJedi76

    BJedi76 Junior Member

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    Truck Year:
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    Truck Model:
    GMC Sierra Classic 1500 4x4 SWB
    Engine Size:
    350”sb
    thank you...
     
    Last edited: Nov 10, 2019
  6. BJedi76

    BJedi76 Junior Member

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    Truck Model:
    GMC Sierra Classic 1500 4x4 SWB
    Engine Size:
    350”sb
    I thought I was replying to a specific post. I guess this is a general reply to all posts.

    Thank you for the “Trapped vacuum spark information” I was unaware of that. I was able to look that up.

    but I was unable to find information on “ locking converter defeat“. what is that?

    thank you...
     
  7. BJedi76

    BJedi76 Junior Member

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    Location:
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    First Name:
    B.J.
    Truck Year:
    1986
    Truck Model:
    GMC Sierra Classic 1500 4x4 SWB
    Engine Size:
    350”sb
    I have been unsuccessful in finding a complete heat stove, nor a working air cleaner housing.

    I can find a new heat stove valve, But not the housing. I suppose that I will have to find a used one or fabricate one.

    I found a few air cleaner housings, but none with a functioning hot air flapper.

    Any parts sources for heat stove housing & functioning Air cleaner housing, would be appreciated.

    thank you...
     
  8. Turbo4whl

    Turbo4whl Junior Member

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    Truck Year:
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    Engine Size:
    350
    The converter lock has a tip in switch on the firewall that is the main control. At about 12 or 13 inches of vacuum the switch closes and current to the solenoid locks the converter. When the vacuum drops to about 8 inches the converter unlocks.

    This system has two defeats. The vacuum is drawn from the manifold then runs through a thermal vacuum switch on the top of the intake manifold, or on the top of the engine thermostat cover. When the engine is very cold no vacuum passes through this thermal switch (valve).

    The second defeat or shutoff is the electrical switch on the brake pedal.
     
  9. Turbo4whl

    Turbo4whl Junior Member

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    This is common, the valve fails and the heat stove will not work. Get the housing with the bad operating valve. Using a chisel or drill remove the spot welds that are on the valve holding bracket. Install the new valve, then weld, screw or pop rivet the bracket back on.
     
  10. BJedi76

    BJedi76 Junior Member

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    Engine Size:
    350”sb
    i assume that, when you speak of this “converter lock”, you mean, the transmission, when you use words like “solenoid” & “current”?

    i wonder if this “locking converter defeat” thing, is why my truck lurches at stop signs or lights, when it’s still a little cold?

    i’ve no idea what year my 700r4 transmission is. anyone know where i look to find out?
     
  11. Turbo4whl

    Turbo4whl Junior Member

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    Yes, I am referring to the transmission locking converter.

    I am sure a heat stove air intake will help with the cold engine. You should continue looking for the parts needed to add this back on the engine. All these cold run items were needed to have a smooth transition from cold start to full engine temperature.
     
  12. 73c20jim

    73c20jim Supporting Member Supporting Member

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    First Name:
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    Truck Year:
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    Truck Model:
    C20 2WD Custom Deluxe. C10 2WD Base Model
    Engine Size:
    350 CID 195/260 HP Goodwrench crate, 400 CID 2bbl
    Sorry, can't help. It doesn't get cold in SE Arizona.
     
  13. TubeTruck

    TubeTruck Full Access Member

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    Truck Year:
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    Engine Size:
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    So you're looking for al the stuff on my motor :Big Laugh: and yes, it all works. One of these days when I put EFI on it I'll sell it all.

    20190909_083254.jpg
     
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  14. Craig 85

    Craig 85 Full Access Member

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  15. Chevy Tom

    Chevy Tom Junior Member

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    my old truck with a properly tuned carb started fine in 90F or below 0. As long as the choke works fine it shouldn't need adjustment.
     

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