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    Q Jet Issues

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    HeavyChevy77
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    Q Jet Issues

    Post  HeavyChevy77 on Wed Jan 13, 2016 11:25 pm

    Recently my buddy has been bugging to rebuild my carburetor since he did the one he had at home. I finally bought the kit to rebuild it and did it, it was pretty simple and great to learn but now I'm having issues with the car running.
    First I disassembled and cleaned the parts with solvents jet were left in place and the metering rods and power valve were cleaned up.
    The power valve wouldn't hold in place and and to do a lttle holding with a flat head screwdriver to slip the air horn on top.
    Car ran rich , smell of gas a lot, and performed ok.
    Bought an another kit, brass float and plastic ring that holds the power valve in place.
    Upon float setting I found out I overlooked setting it (8/32 vs 15/32) since I though it ran good before don't mess with the float setting. I replace the float with a brass one and set it replaced the seat and needle with new ones (the old needle's tip had broke off)
    After all that the car ran pretty good and was happy with it.
    Then at work it was slow so i thought ah ima set the timing I haven't done it yet and noticed a vacuum hose unplugged in the rear, plugged it to its port and it ran a lil rough set the timing and still rough.
    Next morning started it and to 3 starts to get it to idle then pulling around the corner 1st was ok but 2nd it fell on its face and would not go, to it back and parked it has not moved far since.
    I set the timing fluctuating at about 15-16"of vacuum (haven't tuned it yet just both 3.5 turns out) then set it at the stock 8btdc ran poor , throttle snap showed and hesitation with a slow rolling rpm rev
    Set at 4btdc ran ok then poor after a little while
    Then set it to maybe 13 btdc ran real good great throttle response said f*** it tightened the dizzy and told my friend with me let go around the block and upon closing the hood damn idle changed and died by the time I went to put in gear.
    Will be pulling for a clean and inspection and suggestion would be great thanks.
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    HeavyChevy77
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Sat Jan 16, 2016 12:03 pm

    Pulled the carb for disassembly and cleaned it up.
    Noticed a small gold debris, resembles the color of the new brass float No hope the float won't do that more looked for flaking and nothing on the float.
    Float level was good and went to assemble but lost the power piston spring when I was shooting carb clean through the orfices ,remembered look at the spring and saying ah I'll leave it (lesson learned Neutral )
    When to the junkyard early in the morning and just my luck there was a qjet already apart with the power piston,spring still attached, just laying on the intake.
    Went home put it back together and tested it right now and it's all good again.
    Still gotta set the timing and tune but it's running strong.
    But what you guys think cause the issue scratch debris?
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    Myloth
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    Re: Q Jet Issues

    Post  Myloth on Sun Jan 17, 2016 8:30 pm

    Could be cheap parts some of the kits they sell today are junk, gaskets and parts included. And it's nothing new

    more than 10 years ago I bought a parts store Qjet kit that was junk and had to order another name brand to fix it.

    And I have seen brass floats that flake from some kits and I don't know if it's faux brass or what but I have

    just had residue in a rebuilt Qjet not too long ago only after a few test runs?

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    HeavyChevy77
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Sun Jan 17, 2016 10:33 pm

    Got the first one of carbs unlimited (carburetion.com) the second was acdelco.
    Can runs good cruising a slight initial throttle hesitation and goes flat on wot.
    Gonna do some testing Tuesday, my day off, of course after timing is set and tune is done.
    Though the last thing u said is worrying me since I just pumped gas and now runs a hair rougher No
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    Re: Q Jet Issues

    Post  Myloth on Mon Jan 18, 2016 4:35 pm

    If it's idling ok I wouldn't worry too much WOT is usually just tuning whether its the carb or timing

    If you can get it to a minimal bog maybe  the biggest impact for me @ WOT were replacing every

    vacuum line and replacing the distributor which got rid of a lot of WOT issues. oh also fuel lines and pump

    didn't hurt is all that checked it might not be the carb just weak spark? If it all good well then maybe

    you got a leaky air horn they do warp did you check for warpage?

    My own solution for Quads though is to buy a Edelbrock easy to tune and rebuild it's getting hard to find

    good Quad cores these days. But I don't want to knock it when Quads run right they beat anything else

    for street driving.
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Mon Jan 18, 2016 10:44 pm

    I drives pretty damn smooth pulls good except the off idle stumble sometimes.
    Manually shifting it pulls a lot better just stop going above 3500ish rpm. (no tach) falls on its face so maybe weak spark due to cylinder pressures blowing out the flame. My buddy did give me a msd coil and ICM to slap in so just assuming it's ok , but u know what they say about assuming. Also I didn't have WOT issues before so maybe it is the spark, probably pulgs fouled big time from when it was running super rich about 3000 HC with a Cailfornia grade CAT Embarassed
    Gonna time it and tune it tomorrow, I'll post how it went , might order new denso platinum plugs off RockAuto
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    Myloth
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    Re: Q Jet Issues

    Post  Myloth on Tue Jan 19, 2016 1:45 pm

    Before I replaced my distributor and vacuum my plugs were fouling every 100 mi.
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    HeavyChevy77
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Tue Jan 19, 2016 6:14 pm

    No luck today set the timing to stock and drove like a dog no power except if u peddle it gingerly. 19" of mercury tight vibrating needle even with idle screw adjustments.
    If I advance it it runs ok, slight off idle stumble but WOT falls on its face.
    Seen I slight amount of smoke coming from a center bolt hole on the intake so will be replacing the gasket.
    Pulled up to park on a hill and stoping in gear it slightly cutting out like the fuel was sloshing around too much.
    May be float related does the needle and seat combo make a big difference in performance since I used the one in the kit , I'm not sure if it's the right one for my application.
    Also read that I shouldn't have replaced my float with a brass one , apparently they behave differently and have subtle precise differences in the float arms.
    Any sugg. Are appreciated but intake gaskets, and new float are in my future.
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    Marx3
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    Re: Q Jet Issues

    Post  Marx3 on Thu Jan 21, 2016 7:23 am

    If you are running a stock HEI, you will definitely benefit from setting the timing in idle to 10-15 degrees. ( with the vacum advance disconnected )

    Most aftermarket rebuild kits are not worth the money.
    I suggest you spend another 45$ on a proper high quality rebuild kit from cliffshighperformance.com.
    It will contain everything needed, including a new float.

    What is the carb ID number? ( 7 or 8 digits stamped vertically on the drivers side of the carb )

    In order to complete a rebuild, you have to clean out below the idle tubes. They are tiny brass inserts, right beside the venturi's.
    Let me know if you are going to rebuild it one more time, I'll help you out with pictures and descriptions etc.
    Wot issues usually come from the front vacum can being defective and/or the spring for the secondary air valve, being too loose.
    A properly rebuild Qjet will run flawlessly everywhere... From idle to wot.
    I have done Qjets for 10 years. Glad to help, let me know!
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Thu Jan 21, 2016 12:06 pm

    Hey Marx3 appreciate the offer, I was gonna buy a float its gonna end up 20$ w/shipping so might as well get the full kit.
    The carb # is 17057504.
    I was getting fed up with the carb and am looking at an edelbrock replacement , I know they are good dependable carbs but so are qjets and would really like my original carb on putting in work again. bounce
    Thanks for and pics you send and I'll post some my self when I take it apart again, third time is a charm right?
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    Re: Q Jet Issues

    Post  Marx3 on Thu Jan 21, 2016 1:26 pm

    Thats a fine unit. If you treat yourself to a pair of metering rods ( 10$ ) you can take full benefit of a feature called Adjustable Part Throttle, that this unit has. Easy to deal with and very effective when adjusted correct.
    An Edelbrock IS a dependable replacement, but nothing beats a Qjet. Besides, how much will an Edelbrock set you back, compaired to the cost of a top quality kit and a pair of rods?

    Call Cliff ( or write him an email ) and give him the carb number. He will advice you on jet/rods if he thinks it is needed for you application.
    My own '79 caprice with a 170 hp 350 runs strong, has flawless response everywhere and gets 19.5 mpg.
    Seriously, let me know when you want advice and I'll run you through it.
    Obviously, you already know what's inside the carb. Sounds like you just need a couple of hints regarding final tune.
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    Re: Q Jet Issues

    Post  Myloth on Thu Jan 21, 2016 4:12 pm

    Hvychey77 I'd take Marx3 advice on the Qjet as he sounds like he knows more about them.

    I wouldn't knock an Edelbrock though I bought a used 1405 for 100 and rebuild kit for 25 and man choke.

    and I drive my 79 impala daily in the winter time (other day it was 5f) it starts

    and drives me all day with 15-17mpg. Not to be testy I fell in love with AFB style carbs years ago

    when I had 63 Buick daily driver so I am a fan of AFB carbs.

    I agree 10-15 degrees is perfect I am running 11 degrees of timing and I get 18-19hg and idle 700rpm warmed up.
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    hugh.stone.rocket
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    One more thing to consider.

    Post  hugh.stone.rocket on Sat Jan 23, 2016 2:34 am

    I messed around with my carb once and had similar issues. Turned out to be a loose vacuum line. Your carby could be ok.


    Sorry if it don't help ya

      Current date/time is Tue Jun 27, 2017 8:15 am