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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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    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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    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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    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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    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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    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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    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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    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
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Tue May 29, 2018 1:07 pm

    Well forwarded a year still having carb issues had a whey from national carb and was running 100% turned idle screws in to touch and back out never ran right again/low sloppy poor idle
    Orig qjet rebuilt 2x still not right / good idle poor probability
    Edel 1400 amazing perf 2 month later vac leak at throttle shaft smh
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Wed May 30, 2018 6:51 pm

    Checked timing was spot on 10 btdc,my max for emission reasons, idles at 850 19" hg steady no drift vibration but still not silky smooth idle but smooth still
    Exhaust has a slight poof idling , sort of like a bad sealing exhaust valve. Drives well cruising around just can't stuff it as it'll load up or the secondary opens to fast idk look I g for suggestion I was thinking a vac leak but I had resealed it already suspecting that with edelbrock gasket and coated in fipg (form in place gasket) Toyota stuff rec by another Chevy guy , stuff is cool dries like rubber

    Open to thoughts suggestions thanks
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Sat Jun 02, 2018 4:01 pm

    Messed w the carb again tightening the tv cable yielded too late harsh shift so I ended backing off the starting point and helped a little . had issue of @ wot @ freeway speed wants to downshift to 2nd @ 50-60 mph. Lighter line pressure resolved this issue.

    Went to a area to see if it'll break the tires and loads up when tires barley break loose keep holding it'll die gotta stab let go stab let go till it idles by its self after a few seconds. So I started to mess with the air valve tension screw and think it was too loose I went 1/8 then 3x times more after test runs and now doesn't load up too bad at wot but still feel it less power and accel then when I back off the throttle a 1/4. I tried breaking the tires and started to spin/smoke em for a couple seconds but then loads up again and will stall if held. Then tried sliding around doing donuts 1 way then the other ..no prob no stalling ..cruises smooth good around town sounds clean and burbly but still lacking some ponies .

    Tried wot at dead stop it'll chirp the tires but feel like at 2-3 k loads up a little and then clears up.
    I'm could bump timing but then won't pass smog check and feel that's like a bandaid at this point/ timing at 10 btdc with. A new dizzy plugs wires
    Young buck working on technology 2x my age
    Trying to get it running like a dream as it was before.
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Wed Jun 06, 2018 11:48 pm

    Pulled the plugs today # 6 had a little white build up(toohot?) but mostly clean / #4 had some dried oil build up on the electrode / all other plugs clean white

    Changed the 2 plug and messed with. Air valve screw tighter and loosened the tv cable another hair helped a lot didn't feel so flat accel and downshifted better @ wot but ...still feel something a miss under a big load the engine feels like it's fighting its self .. Sound like vooh vooh vooh (sputter) and I let off a little and sounds and accels better
    ...also now breaks tired better loads up when @ wot
    Stopped at idle for a little bit and I stuff it breaks the tires loose but loads up just when it starts to pull away strong .

    Any advice??
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Fri Jun 08, 2018 11:20 pm

    Adjusted air valve got to the point it was locking the secondaries out , backed off some and was the best perf but not what I want . tightened the tv cable a hair helped some.
    Enough squawking here's some vid
    https://youtu.be/RpJ6SgNJvIc
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Sun Jun 10, 2018 7:38 pm

    https://youtu.be/UJcsyocrAp4
    Engine in park
    Still not right feels a misfire probably the #4 cyl chokes at wot but letting off and back on helps keep the power going.
    The holley I had on was poor off the line then woke up past 40 then u can be rolling 60 let idle stuff it no bog
    Noticed more power top end w the holley so I know the engine can make good smooth power at wot high rpm
    Any thought might end up using the holley and experiment with pump cams.
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Fri Aug 10, 2018 11:30 pm

    So Holley had an issue that was not tunable so back with the qjet
    Suspected internal vac leak and removed intake.
    Found a tear in the gasket at the lower port of cyl 4 that was oil fouling. Replaced gasket ran a week and removed the plug ....white like snow (ran the Holley agin same issues/poor driveability 1/8-1/4 throttle open FLAT spot)
    So did a basic adjust of the qjet.
    Cruises great snappy throttle response/revs mean in park ...buuutt has no power up stairs, the trans may be slipping I've played with the tv cable got smooth shifts but in normal or manual shift through 1st and 2nd then open the throttle half feels good tip a hair past 1/2 and power dips off as if the clutches are slipping in 3rd it feels good I can put the pedal to the floor and the boat floats past em... I just can't shake my tires loose down the road :'( ..I'm starting to think the th200 is just near the end of its line , because in reverse if I quickly open the throttle the tire break loose and feels a lot better power flow...I'm sure I could do a break stand in reverse but not forward. Sighh....do I just need to swap it with a th350?
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Tue Sep 18, 2018 2:16 pm

    Wow what a can of worms I had opened messing with something that wasn't broken well I solved my issues a long fked journey it's been
    - rebuilt orig qjet /failed no wot
    -gave up got a 1400 edel / ran like a beast!!...but had to use 91 to fight fuel perculation and would seep fuel @ the shaft when hot plus mpg went down and then 3months later grew a throttle shaft leak
    -then got a remain qjet from nation carburetor in Florida /ran perfect ..like a cloud on wheels /set the isles screw in and out again to retune dropped from 21"hg to 15"hg no driveability sent back 3x for a refund in the end.
    -with in those 3x times sent back I took the orig carb to tj Mex to a known carb shop and they "rebuilt" it and got my vacuum back but no wot still
    -so..frustration and desperation setting in I splurged for a reman smog legal Holley , that had issues from the get go spent $ on all the stupid cams and squirters to fix my terrible off idle stumble that was uncureable. Think I was a returned reman for a reason I read on forms that some holleys have this issue
    -well with desperation well settled in I have up went back to national carburetor for another carb hoping I would be perfect again and ...It was just ok ..vacuum was only 19"hg and was the most I could get and the wot didn't feel right I adjusted the air valve spring from tightest to loosest and in between but would give me the perf I wanted ..couldn't even knock the tires loose..
    - so I rebuilt the qjet again figured I had nothing to lose...well I didn't even need to look up how too I remebered where everything when from the last time and took the air horn off found half the idle tube fell out, air horn warped , 2 screws just screw into the main body and 1 was stripped and left loose (vac leak?!) and missing washers on the hardware ...you would think a carburetor shop with years of exp would catch this ...but what was worse was that the reason for poor wot was a missing secondary air valve cam
    I noticed after assembly I saw the metering rods only lifted a fraction of their height compared to the other ...looked closer saw it was removable so took the air valve blades off pulled the shaft and swapped the cam to the orig and bam wot work again and vacuum at 21"hg at 750rpm I can smoke my tires at a stop & spin em off the line .. Happy again but hurt my trans shifting into second a bout 60 mph tried to force it into higher rpm band with the qjet from national carbs ...slips in second gear gotta shift into 2nd manually to have a nice firm 2nd gear...
    Had to cut the original tv cable due to a snaffu when dropping the trans and Jack handle slipped out with pressure release and trans was hanging off cable had to cut to release ..
    Bout a generic one was close enough but not perfect but recently found a orig style from ATP and looks nice gonna slap in tomorrow maybe fixes or helps with 2nd gear slip just enough to pass smog and save/plan for a 2004r swap
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Tue Sep 18, 2018 2:47 pm

    Just wanna give a big a special fuck you to dependable carburetor in Imperial Beach California if u need carburetor work in San Diego Ca go ahead and take these guys off your list..
    Took my carb to these "experts" and told them my issues/symptoms and they just took my money and said ok well call u ..
    Well I had to call them to when it was ready to pick up a half ass rebuild carb
    Had to redo all their shady half baked work
    So if the employee or owner is reading this a nice fuck you to you and have a nice day prick sunny
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    Re: Q Jet Issues

    Post  HeavyChevy77 on Wed Sep 19, 2018 5:46 pm

    *update* eng blew...
    Nah jk (knock on wood)
    Took out the old tv cable that is a universal type for both th350&th200
    Which weird since one is a kickdown and the other a tv.
    I had to cut the old one as stated in the prev post, so got this as I didn't have many options.
    So recently I came across a tv cable specifically for my 77 caprice 350/th200(orig!!) the company is ATP. I have got to say I was impressed with the quality factory fit part and robust sturdy plastic housing not cheap stuff. I got the last one off Amazon(sorry Razz) ATP Detent Cable Y-106 for $6 !
    Took the universal one off and put...well tried to put it in but the goddamn high quality rubber seal was too new/thick I tried working it in but laying on your back I tend to have less patience....so lineman pliers and a grinder I wilted the seal to about half its thickness and gave a wiggle and a push and popped right in.
    Layer her on the ground again went around the block and 1st pulled nice and now 2nd....and no more slipping like it's has neutral for 2nd gear above 3000 rpm!!
    ATP FOR THE WIN!!! Quality stuff I have a trans gasket kit from them and the gasket is thick fiber/paper material and is thick rigid but yet cusiony and they claim no sealer needed.
    Give em a look.
    ATP U GOOD TO ME!!!

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