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  1. #1
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    Default Quadrajet part number 7029282

    Hi guys


    I do not drive my UTE with Holden 308 much. I started it after about a month and found that it did not want to idle smoothly even after warmed up.
    I took her for a short drive but every time I came to a stop it would stall. (Its always idled smoothly before).


    So when I got back I took off the air filter and played with the idle screw and found that when I screwed it in the engine got very rough and shaky, when I backed the screw all the way out the motor would smooth out.


    Any idea why its doing this.


    I am going to be rebuilding this carb soon. Would like to know what to be mindful of when working on it.

    Just waiting for some parts to arrive.


    As always I appreciate all the advice received.


    Kavesh

  2. #2
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    The first thing to do if the carb has not been apart for a long time is to put a kit in it, new needle & seat etc, set float level. I just kitted a QJ today & it helped remind why the Carter Thermoquad is a much better carb....

  3. #3
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    Quote Originally Posted by GtoGeoff View Post
    The first thing to do if the carb has not been apart for a long time is to put a kit in it, new needle & seat etc, set float level. I just kitted a QJ today & it helped remind why the Carter Thermoquad is a much better carb....
    I will be rebuilding it soon as soon as parts arrive.

    Was hoping to know what to look at to sort the idle issue

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    The QJ has horizontal passages in the base of the main body that pass fuel to the idle mixture ports. Being in the bottom of the casting, & horiz, they can build up with sediment over time, blocking the passage[s]. This can cause a rough idle &/or stalling. Need to poke some wire through the passages to clean them out.
    I presume you have checked that the choke is operating correctly?

  5. #5
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    I have been watching some videos on how to rebuild the quadrajet and came across something on the airhorn design on the bottom.

    Now from what the one video mentioned is that on bigger motors or motors that has lots of work done to it, there is a notch on the inside of the airhorn which allows more air in, which in turn makes the motor idle smoother.
    My question is my carb meant to have the notch on the airhorn. My does and I am not sure if that is correct or not. My motor is a stock Holden 308 engine.
    I wish I was able to load pics to explain better but for some reason I cannot, get the message that I have exceeded my quota by 1.24mb. I have not loaded pics here for years probably due to the same message.
    Your advice as always is appreciated.

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    The notch you refer to is for bypass air. Some carbs use it, some don't. The carb base would need to be drilled for it be functional.

    However, I don't see that is your problem because if I am reading your post correctly, it did idle ok, but then the idle got rough. If the base is drilled for bypass air, make sure the holes/passages are open & not blocked with debris or carboned up. Very rare for this to happen.

  7. #7
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    Yes my carb was idling fine before it developed a problem.

    I will give it a good clean and make sure all passages are clear.

    My concern was the notch for the bypass air. If its not an issue with no adverse effects I would be very happy. Was just wandering whether my air/fuel mixture screws would be affected by it. Reason I say is that the mixture screws had little effect on the idle although it did idle fine just could not fine tune it

  8. #8
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    Sorry for not posting here for a while.
    I have finally put a new kit through the carb. Cleaned out all the passages with wire, hopefully I reached everywhere.
    As I do not know the full history on the carb, I am not sure if the parts are original for it.
    Would anyone be able to tell me whether the following is the correct combination for a standard 308 motor. Primary jets 71, primary rods 41 B and secondary rod AM.
    Also what is the correct height for the float measured from the toe end.
    I have put the carb together and it is idling much better, however, I notice that there is a little fuel at the front vacuum port that goes to the advance canister on the distributor.
    Plugs are looking fairly light in colour which makes me suspect that it is too lean. I was told to richen the mix I would need new jets or primary rods. The mixture screws won't be enough, or is that bad advice. (thought the screws were there for that purpose)

  9. #9
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by kavesh View Post
    Sorry for not posting here for a while.
    I have finally put a new kit through the carb. Cleaned out all the passages with wire, hopefully I reached everywhere.
    As I do not know the full history on the carb, I am not sure if the parts are original for it.
    Would anyone be able to tell me whether the following is the correct combination for a standard 308 motor. Primary jets 71, primary rods 41 B and secondary rod AM.
    Also what is the correct height for the float measured from the toe end.........................................)
    All 308 Quaddies, early late had 71 primary jets.. and DP secondary rods
    but.. the problem is that the primary rods changed design.. and are not interchangeable
    by the way, old versus late Quaddie

    GMs Rochester division (Qauaddie manufacturers) say this-

    Although the primary jets interchange between all years of manufacture, there was design change in 1975 and the primary
    metering rods from 1965-1974 (PNs starting with 70) are 0.080" longer than those from 1975-1980 (PNs starting with 170)


    The late (Quaddies starting with # 17..) had a 49P Primary rod but not having my original HQ
    manual at work (who does? ) I cannot tell you right code for that 7029282 Quaddie
    might check tonight ....

    From memory the float measure is11mm or 0.40" taken at the toe.. being the distance BELOW
    the carb body top when using a factory standard float (aftermarket larger or smaller floats will differ)
    Last edited by Smitty2; 24-10-2019 at 10:35 AM.
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  10. #10
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    Quote Originally Posted by Smitty2 View Post
    All 308 Quaddies, early late had 71 primary jets.. and DP secondary rods
    but.. the problem is that the primary rods changed design.. and are not interchangeable
    by the way, old versus late Quaddie

    GMs Rochester division (Qauaddie manufacturers) say this-

    Although the primary jets interchange between all years of manufacture, there was design change in 1975 and the primary
    metering rods from 1965-1974 (PNs starting with 70) are 0.080" longer than those from 1975-1980 (PNs starting with 170)


    The late (Quaddies starting with # 17..) had a 49P Primary rod but not having my original HQ
    manual at work (who does? ) I cannot tell you right code for that 7029282 Quaddie
    might check tonight ....

    From memory the float measure is11mm or 0.40" taken at the toe.. being the distance BELOW
    the carb body top when using a factory standard float (aftermarket larger or smaller floats will differ)
    Thanks Smitty.
    I would appreciate it if you could let me know the code for the primary rods, at least I will know if it is correct.
    My float is set too high then. I set to 5mm, so will need to correct that. But will only get to it once you advise of the primary rod code. I certainly hope that mine is correct as I am in South Africa and getting parts here costs so much and takes a lot of time.

  11. #11
    been here .......too long Smitty2's Avatar
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    the HQ manual gives the early code for the Primaries - 77C
    (.. this is a strange code as far as I recall)
    and also gives the Secondarys code of AN (not AM as you have)

    Curiously I cannot find AN specs in any of my Quadrajet specs and docs
    but i did find find yours here -

    Quadrajet Carb Specifications Page 2 - Route 66 Hot Rod High

    The thing with Secondary rods is.. they need to be matched to the hanger they are on
    some detail here -

    http://peterpam.customer.netspace.net.au/hanger.jpg
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  12. #12
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    Quote Originally Posted by Smitty2 View Post
    the HQ manual gives the early code for the Primaries - 77C
    (.. this is a strange code as far as I recall)
    and also gives the Secondarys code of AN (not AM as you have)

    Curiously I cannot find AN specs in any of my Quadrajet specs and docs
    but i did find find yours here -

    Quadrajet Carb Specifications Page 2 - Route 66 Hot Rod High

    The thing with Secondary rods is.. they need to be matched to the hanger they are on
    some detail here -

    http://peterpam.customer.netspace.net.au/hanger.jpg
    Thanks Smitty.
    That is getting to technical for me now.
    Perhaps my rods are AN and I was not able to read it clearly.
    I am still needing to know whether my primary rods 41 B are correct for the jets 71. Hopefully that combination is correct.

  13. #13
    been here .......too long Smitty2's Avatar
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    ok.. I do not have that much knowledge of the early Quaddies (I can do late model ones in my sleep)
    so
    I have been digging.. mainly on US Chev and GM forums covering 1970 and earlier models.
    Even had a quick review of Cliff's site to see if I can glean more here.

    And yes, I found a number of comments..... that for the early Quaddies, the rod number should be THIRTY
    (30) numbers LESS than the primary jets. That is 71 jets use 41 primary rods, 72 jets use 42 rods etc.

    I found lots of stuff like this ... If mildly modified maybe try a 73 jet and 44 rod

    Yours is not modified .... so to start, go with the 41/71 primary combo and see how it starts,
    idles and performs
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  14. #14
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    Quote Originally Posted by Smitty2 View Post
    ok.. I do not have that much knowledge of the early Quaddies (I can do late model ones in my sleep)
    so
    I have been digging.. mainly on US Chev and GM forums covering 1970 and earlier models.
    Even had a quick review of Cliff's site to see if I can glean more here.

    And yes, I found a number of comments..... that for the early Quaddies, the rod number should be THIRTY
    (30) numbers LESS than the primary jets. That is 71 jets use 41 primary rods, 72 jets use 42 rods etc.

    I found lots of stuff like this ... If mildly modified maybe try a 73 jet and 44 rod

    Yours is not modified .... so to start, go with the 41/71 primary combo and see how it starts,
    idles and performs
    I also tried to check with Cliff and he did not recognize my carb number. His database is limited to USA carbs I suspect.
    Ok, then for a start all I need to do is reset my float level to 11mm.
    My jet and primary rod size is correct then.
    So besides enriching the mix by going with a larger jet or smaller rod, what is the main benefit, all I see is more fuel being burnt.
    Yes my 308 is stock standard.
    Hopefully this will be the last time that I open up the carb for many years..
    I still need to verify the secondary hanger though, just to make sure it is correct for the carb. I do have a couple of spare parts from a junk carb of the same part number as mine, which incidentally had larger jets in. This carb was originally in a Monaro / Chev SS 308 motor.

  15. #15
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    Just a quick update, adjusted the float level to 11mm. Motor seems to run fine, although the idle screw is backed off completely and the idles slightly higher than what I would like. This condition was always present.
    While reading a post on the Hotrodders forum I came across the statement "Be sure you are idling on the idle circuit and not on the primary"
    How would I determine this? I know the choke is completely off as i backed off the fast idle screw.
    I may just be getting paranoid a little I think.

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