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Hesitation

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ryder, Nov 21, 2002.

  1. ryder

    ryder Registered Member

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    I have heard my entire life that the older vehicles were the simplist to work on, funny thing is that I am only fimiliar with newer ones.(and motorcycles) Just picked up a 73 jimmy with a 350 from my dad, he had pull the old carb off,so I purchaced a reman. q-jet. I was told that the idle screws should not need to be adjusted. But just off idle there is a signifigant dead spot before it starts running out well. I checked the timing and it was advanced two degrees, I put it back at zero. No luck there. I decided that I will leave it there until I figure the carb issue out. Points,cap,rotor,wires and plugs are all good. The choke seems to be hanging up a little, it only opens about 3/4 thus not allowing the secondaries to open either. That will be solved tommorrow, but I was courious if that would cause the off idle hesitation? and if not what might it be?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    If you are trying to accelerate hard, yes, no secondaries could cause problems. If you have the problem any time, then probably not the secondaries.

    Idle mix screws are for just that, idle. You MIGHT try playing with timing, I never compared mine to "stock" timing, but I'd get a nasty bog off-idle if my timing wasn't to the liking of the engine. Nice carb backfire too.
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Timming should be at 4-8 depending on the year. My 75 is 8 as is my 79 with HEI.
    A off idle bog in a Quad is usualy a bad acclerator pump.
    Take the aircleaner off. on the driverside front of the carb will be a rod sticking up with a lever that goes down to the throttle linkage. Thats the Accelrator pupm stuff.
    Get a light and shine it down into the carb and prop open the choke if it's closed. While looking down into the primary bores give the accelerator a turn. The rod should get pushed down and you should se a squirt of fuel shoot into each bore from a port on the wall of the bore.
    No squirt or just a dribble then something is wrong with the pump. Either the rbber part of the pump came off or the check ball in the bottom of the pump bore is not there or jammed open.
    Since it's a rebuilt take the POS back and make them give you another one. If the box the rebuilt Quad came in says "Holly" on it anywhere then expect to go throught 2-3 before finding a decent one. They have horrible QC.
    As for not needing to adjust the mixture....BS. The mixture needs to be matched to the engine and there is no way to do that without it being on the engine it is going to be used on. Yeah new you can match because all the engines are new but even so they can be fine tuned.
    Best way to set Idle mixture is with a Vacuum gage. The higher the vacuum your pulling the more efficent the burn. I always give a 1/8 turn lean to help with altitude and barometric changes.
     
  4. imiceman44

    imiceman44 1 ton status

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    I second everything Grim just said. /forums/images/graemlins/thumb.gif
     
  5. Muddytazz

    Muddytazz 1 ton status

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    Grim, whats the easiest way to adjust the air/fuel mixture...mine is running super rich. /forums/images/graemlins/shocked.gif
     
  6. imiceman44

    imiceman44 1 ton status

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    Grim correct me if I am wrong here but IIRC the 2 screws on the bottom of the carb (idle mix screw) you back out to lean turn in to enrich. I would go half a turn at a time, and I use the vaccum guage all the time because you can't go by anything else if the engine is modified or tired, max vac is the best technique. I keep going out as long as the vac is going up. When it starts going down, I start turning it in until it starts to go back down again on the other end and I back it half a turn.
    I hope I didn't confuse you here.
     
  7. ryder

    ryder Registered Member

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    well Grim you were right... accelarator pump. Traded it in for a q-jet that wouldn't keep fuel in the bowl overnight. spoke to a fella at holley's tech line and he assured me that if the next wasn't to my satisfaction that he would make sure a "good one" was built and get it shipped out to me. Pretty upsetting to know that they have to custom make functional carbs. /forums/images/graemlins/mad.gif
     
  8. imiceman44

    imiceman44 1 ton status

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    Exactly... /forums/images/graemlins/mad.gif
    And what really upsets me is when you get the lifetime waranty, and you have to keep trying to get a functionning part, they are using us for quality control. /forums/images/graemlins/ooo.gif
     

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