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Carb or Engine gurus??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SCOOBYDANNN, Dec 3, 2001.

  1. SCOOBYDANNN

    SCOOBYDANNN 1/2 ton status

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    W/ the truck warmed up when at idle, if i stomp on the gas there is a studder, an empty spot, like not rapping out evenly only at the beginning. if i slowly lay on the gas it dosn't do it, only when i stomp on it. My somewhat educated guess is either the carb or timing. Can anyone help me?

    p.s. i have a mild 4x4 cam and quadrjet, don't know timing cause i have no timing tab

    Sun Desert Offroad <a target="_blank" href=http://4x4.alloffroad.com>4x4.alloffroad.com</a>

    It's all fun and games till somone loses an eye!
     
  2. Thunder

    Thunder 3/4 ton status

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    Sounds like your guess is pretty close. First with the engine not running look down the throat of the carb and pull back on the throttle linkage. You should get a good healthy squirt of gas down the primary(small holes) carb throat. If you dont get a good stream of gas as you pull back on the accelator linkage..the accelarator pump is bad in the carb. That will cause a bog on acceleration.
    If you are getting a good squirt of gas the timing may be off.
    If the timing is too far retarded it can cause a bog , lack of power, bad gas milage,
    If it is too far advanced it will ping and can backfire.
    You said you dont have a timing tab. you really ought to get one so you know your engine is properly timed.
    If you have a vacume guade you can set the timing without a timing light or a tab.
    Hook up the vacume guage. With the engine at idle. Move the distributor till you get the highest reading on the guage. Leave the distributor at the position where the highest reading was obtained and tighten it down that usually gets the timing very close to where it should be

    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze>http://coloradok5.com/gallery/Thunders-Blaze</a>
    <font color=blue>NEVADA: Where the pavement ends, and the West begins.</font color=blue>
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Get a Holley!
    With the problem your describing it sounds like the accelerator pump..
    If you had a Holley you can get the assortment of like 10 different accelerator pump cams, and dial it in until that off-idle sputter is gone.
    It's when you stomp on it quick, it opens up those butterflys, and the accelerator pump can't squirt enough gas to compensate for that temporary lean condition.
    Don't know what to say about that Q-jet.
     
  4. Twiz

    Twiz 1/2 ton status

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    Cold weather? Did this condition happen when the weather changed? Or does it do it even after a high-way driveing? (totaly warmed-up) -The answers could help diag. the problem, could be timing or fuel rellated. Fuel related problems could occure when the temp changes. Timeing probably would happen all the time, regardess of the temp.

    Excellerator pump-shot problem: Whan you stomp on the gas- hard, it would go way-lean. Because, air will flow faster than fuel and the feul will condinsate on the port walls, that is all-ready in the ports. So, the excellerator pump adds more fuel "right-now", to cover up that lean condition. To check- as stated above- work the thottle by-hand and check for the pump-shot.

    Also, check for a vacume leak. Check hoses, gaskets and the throttle blades for play. Any vacume leak will also cause the sys to go lean- and might have the same effect, all the time, but when cold it might be exaggerated

    <font color=blue>Twiz</font color=blue>
    Can't get it up?
    So, drop it in
    gear.
     
  5. k5ntexas

    k5ntexas 1/2 ton status

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    i'm having a similar problem and what does the squirt of gas look like? just wonderin. thanx in advance. later.

    jacob

    what is that low rider doing under my k5?
    wow nice lil jap car. whats it good for?
     
  6. Twiz

    Twiz 1/2 ton status

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    Q-jet? If so. From the top, look into the choke tower, open the choke (if closed) look inside, there are 2 screws inside the choke-tower, just about a 1/4 inch in (towereds the center) are the excellerator pump shot out-put ports. They are very hard to see. Work the thorttle by hand, with the float bowl full, there should be a solid shot of fuel, just like a squirt-gun, aimed at the boosters.

    Sorry Thunder, didn't mean to steel your -um- thunder, but I'm on the subject my-self. (and need the post count to keep up with Pureinsanity)

    <font color=blue>Twiz</font color=blue>
    Can't get it up?
    So, drop it in
    gear.
     
  7. k5ntexas

    k5ntexas 1/2 ton status

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    ok thanx. i'm gonna look at it this weekend. i ain't got time. if i got any questions i'll post and see if i can't fix this thing to run at its peak mpg with good enough power. i wanna fine tune it so i can save as much to get my 383 stroker. thanx again. later.

    jacob.

    p.s. when i get my 383 i'll become a member. thats a guarantee. lol.

    what is that low rider doing under my k5?
    wow nice lil jap car. whats it good for?
     
  8. SCOOBYDANNN

    SCOOBYDANNN 1/2 ton status

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    Cold-Weather--no it was doing it before it got cold, it only does it at idle and i stomp on it. I can even go kinda fast and it won't do it, also when im actually driving it and have to switch gears it does it. im gonna check the things you told me and hopefully get it fixed. also, if i let the truck sit overnight (mostly sits for a couple days though) it takes a good while to start (like 2 turns for 10 sec and usually starts on the 3rd) could that be a symptom also?

    thanks

    Sun Desert Offroad <a target="_blank" href=http://4x4.alloffroad.com>4x4.alloffroad.com</a>

    It's all fun and games till someone loses an eye!
     
  9. marv_springer

    marv_springer 1/2 ton status

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    Danny,

    Those are 2 separate probs - but you can fix them both when you pull it off....

    The sitting/hard starting thing is cuz the float bowl is drying up. Typically leaks out the well plugs at the base of the float bowl. JB Weld the plugs to stop leakage.

    As far as the stumble, replace the accelerator pump and put the rod in the shorter hole on the lever arm for max squirt.

    Oh, and don't get a Holley!

    Marv
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    <blockquote><font class="small">In reply to:</font><hr>

    Oh, and don't get a Holley!

    <hr></blockquote>
    They do make good wheel chocks...[​IMG]

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  11. zakk

    zakk 1/2 ton status

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    unless you actaully enjoy replaceing the power valve everyday!

    -zakk

    '77 1-Ton K5

    [​IMG] CK5's MOAB 2002 OR BUST!! [​IMG]
     
  12. mudmover

    mudmover Registered Member

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    if your accel pump seems to be working, you can also check the choke pull off too. if the secondary flaps open (the ones on the top of the carb, over the secondaries) immediately instead of gradually the sudden rush of air will lean it out and cause a bog. good luck to you. Oh, and put my vote in for not putting a holley on your truck too. great for a race car, but sucks for a 4x4. (too easy for the fuel to spill out of the vent holes and stall your engine.)

    Mudmover

    What do you mean you cant run <font color=red>35's</font color=red> and an <font color=red>easy locker</font color=red> and <font color=red>3:08's</font color=red> in a <font color=red>10 bolt</font color=red>?[​IMG]
     
  13. 1986Blazer

    1986Blazer 1/2 ton status

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    OK, great post guys. I have a similar problem. After I start my rig, in the morning, I can drive a few blocks and everything is fine. But, as soon as I stomp on it, like after a slow California Stop, it bogs down, seems to back fire a little but will accelerate fine once I back off the gas. After warm up, it runs fine and does not bog down anymore. The Qjet is a rebuild from a very good shop. Timing is dead on and I have a new HEI Accell Distributor. Thanks for any info.

    <a target="_blank" href=http://www.geocities.com/keywestk5/KeyWestK5.html>http://www.geocities.com/keywestk5/KeyWestK5.html</a>
    So I says to him, I said, "get your own monkey."
    1986 K5, 350 GM Crate, 700R4, NP208
     
  14. SCOOBYDANNN

    SCOOBYDANNN 1/2 ton status

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    Tell me about the Holley---ii hated that darn thing. so everyone seems to agree it's the carb. I have a warranty w/ autozone w/ this one--should i go get a "new" one or shuld I try and open it up?[​IMG]

    Sun Desert Offroad <a target="_blank" href=http://4x4.alloffroad.com>4x4.alloffroad.com</a>

    It's all fun and games till someone loses an eye!
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Get rid of it. I absolutely hate Holley carbs just from working on them at my old job (I worked on boats).

    Every one of them that isn't used for drag racing (WOT all the time) is a worthless hunk of crap.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  16. michaelm

    michaelm 1/2 ton status

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    how often does your POS backfire and kill powervalves?
    just for you, holley sells a kit for people with dead engines that back fire a lot.
    I have NEVER had a dead powervalve, and i only run Holleys
     
  17. BlazingItaly

    BlazingItaly Registered Member

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    Anybody tought about the choke pull-off, mine was stuck and the choke plate wouldn't open even when warm.

    just my tought

    Luca
     
  18. marv_springer

    marv_springer 1/2 ton status

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    Try the warranty swap.... If they'll do it, that would be quickest!

    ...sides, you don't need to spend your time building carbs.... you got a 'cage to build!

    Marv
     

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