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Help the Fumes are killing me!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tc81k5, Jun 18, 2003.

  1. tc81k5

    tc81k5 Newbie

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    I've read all the posts on tuning a q-jet on this site but right now I don't know where to go next.
    rebuilt 305 installed 6 months ago
    Original Q-jet that was rebuilt about 6 months ago. I can't seem to get rid of the "rich" smelling exhaust and smoke(black/blueish). I set the timing and idle and back out the screws to highest vacuum reading. I'm steady at about 17 in/Hg. I took air horn off last night and checked float setting. It actually appeared a little low so I raised it to the 15/16 in(stock setting).

    I also noticed when I put the vac line back on vac advance timing retards to about 12 or 13 BTC. This goes back to the question of whether the vac advance should have vacuum at idle.

    I'm going to pull a compression test tonite.

    Any ideas will be greatly appreciated
     
  2. bigblock44k5

    bigblock44k5 1/2 ton status

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    Location:
    Hurlburt Field, FL
    if the smoke coming out it blueish, then it is oil burning. vacuum advance should have no vacuum at idle. when it gets vacuum it should not retard though, it should advance. you could try leaning out the mixture screw a little bit more to see if it will stop smoking.
     
  3. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    93octain will make the fumes smell better /forums/images/graemlins/thumb.gif
     
  4. tc81k5

    tc81k5 Newbie

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    I like your "If it ain't broke, fix it til it is". This truck has fought me tooth and nails ever since I bought it off the original owner last fall.

    I'm trying to give it some TLC and it "the Boll Weevil" doesn't appreciate me.
     
  5. the professor

    the professor 1/2 ton status

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    I would be willing to bet, that the main well, secondary well or power valve well plug(s) are leaking...

    It is also possible that the "float sunk"
    --
    Does the engine crank alot when cold... act like it ran out of gas, then starts suddenly and runs ok..??
    --
    A sure fire way to check for leakage... is to let the eng sit for a day or two... and pull the top off the carb...
    -
    If the float bowl is empty, or low... you are leaking.. This is a pain in the butt, and will probably ruin the gasket.. so do it the easier way..
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    Pull the carb, remover the rear two screws in the air-horn.. flip the carb (watch for spilling gas)... pull the other three screws from the carb base...
    --
    You will see 3 major "bosses" sticking out of the carb body... 2, have about 1/4" flat alum plugs , 2 have small lead/alum plugs, and the third has 1 alum/lead plug
    --
    They will usualy look as if they are leaking, but maby not...

    Clean the area with brake clean, lightly sand the plugs and bosses, and coat with JB Weld Epoxy.. (I like that, it takes 600deg reather that the 250-300 or regular epoxy) Be VERY careful, not to get into the gasket area.. also watch for crap going into the various passages when sanding...
    -
    You can reuse the lower gasket with no problem if fairly new...

    Let sit for at least 16-20 hrs the install and run.. If fixed no problem
    --

    Sometimes the floats, which are phonelic resin (a type of plastic)... saturate with fuel over time.. and get "heavy"..

    If this happens, even if the float level is correct, the fuel level will be high, and it will run rich at idle, and start hard, or with smoke hot...

    ALWAYS replace the float during a rebuild.. they only cost about $10
    --
    Both problems will run about the same way hot, rich or slightly rich idle, poor fuel milage, and can "load-up" and flood, when you do a "hot-start" but usualy act different cold..

    THe leaking carb, will act like it ran out of gas when you try and start it after sitting for awhile, like overnite, or for a day or two... This is because it actualy has.. the float bowl has drained into the engine...and has to be filled before it will start...

    The heavy float, usualy starts normaly cold.. because the float bowl is full, sometimes over full

    Earlier carbs, pre 1973, all teneded to leak in the secondary wells... the rebuild kits, even the factory Delco ones, had a dense rubber pad that whent into the base, and pushed on the plugs...

    They were redesigned, and the gasket and casting are supposed to isolate this area even if it leaks..it rarely works..

    The later carbs tend to leak at the smaller plugs.. the two at the jet wells

    These two problems are usualy what gives the Q'jet such a bad rep... people rebuild them and they still run like garbage... /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
     
  6. 88Silverado

    88Silverado 1/2 ton status

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    Location:
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    Prior to 1971 (I believe) the factory standard for vacuum advance was full time vacuum port. This brought the advance up to 30+ degs at idle and under little load (cruse) and was more efficent but was bad for emissions (really stunk at idle).
    After 70, they moved the vac adv to the timed port (where no vac at idle, only when throttle plates are cracked) this helped emissions quite a bit and makes the car stink less, however, this setup can cause a vehicle to ping easier under load which isnt good for the engine.
    Disconnect the vac adv and plug the carb port when you set initial timing, then connect it up.
     

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