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  1. #16
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    After the float level was adjusted to 11mm, I was only able to take the vehicle for a ride yesterday. What I have noticed is that there is now a hesitation on rapid acceleration. This was not the case when the float level was higher.
    I went for about a 30km drive mostly open road cruising around 100-110km/h. Looking at the plugs after the drive they are rather light in colour very light brown indicating a lean condition.
    Would you suggest raising the float or possibly going with a larger jet. I do have 76 jets that I could try.
    Really bummed that I have to open the carb again....

  2. #17
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    Float level setting depends on two things:
    - fuel pressure
    - needle & seat orifice size

    Change either of these & the FL will need changing. A larger n/seat than what was factory fitted will require the FL be increased, ie the float will sit lower in the bowl. Lower fuel pressure will require the FL be decreased.

    Carter published a chart showing how to set correct FL for it's carbs for various combinations of fuel pressure & n/s size. It is an eye opener. Quite a variance with pressures & seat sizes.

    As for the QJ. My Motors Manual that covers 1972-78 list FLs anywhere from 1/4" to 15/32". Cliff Ruggles maintains that 1/4" is the correct level for overall use. A change in fuel level of about 0.100" is worth one jet size.

  3. #18
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    I am running the standard mechanical fuel pump. Its old so cannot confirm what pressure its pushing out.
    The needle and seat I got from the kit ordered from Quadrajet Power in the USA. Again I cannot tell if its the same or different to what was there before (I suspect Quadrajet Power supply high flow needle and seats with all their kits.
    Wow, I never knew that the float level would impact your jet size like you mention. So by me dropping my float level by 5mm I effectively changed 2 jet sizes smaller. This may explain my lean condition and hesitation.
    With the float level higher as mentioned in a previous post I was getting fuel out the vacuum advance port, with the lower level there is none.
    I think I will try bigger jets with the same float level. I have 76 jets. (Btw, I was going through my jets and primary rods and realised that what is installed in my carb is 71 jets and 45B primary rods, not the larger jets.) They are so damn difficult to read so messed up. The 76 jets and 45 rods will be close to the 30 difference for my standard motor, hope the float set to 10mm is fine.

  4. #19
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    I doubt the float level caused fuel to exit the vac adv port, more likely flooding.

    I had another look in the 1972-78 MM. Buick QJ #17058540 used a 7/32" f/level. That is less than a 1/4". Many Pontiac models had 17/32" f/levels, over 1/2". 7045263 & 17058266 are examples, & different year models.

    That is more than a 1/4" spread in float settings....

    As far as I know, the internal height of the primary discharge nozzles was the same for all QJs.
    The Ruggles QJ book says this on p.83 about FL: " The float ht should be set to stock specifications for stock rebuilds. If the stock settings cannot be found, set the float to exactly 1/4 inch for all models."

  5. #20
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    I am reviving my old thread on the quadrajet.

    Just a recap, my carb was rebuilt using a Quadrajet Power kit in 2019, was never entirely happy with it but that was more due to engine issues which have now been resolved, so I am back to sort out the carb.
    When I opened up the carb the internals had the following, 76 primary jets, 45B primary rods and AN secondary rods on a B hanger. Float was set to 10mm
    I found that the motor was very heavy on fuel.
    After reading some posts on this thread again and other information on the net, I found that the carb originally had 71 jets, but could not find what the original primary rods where.
    I have changed the primary jets to 71 and used the 45B rods.
    There is a little bog/hesitation when taking off which was not there before. Took the UTE for a 120km drive and must say that my Holden 308 performed beautifully. Even going uphill feed a little on the accelerator and it picked up speed nicely. I have never seen her perform like this before. Motor idles pretty steady, but a little on the high side, have not fine tuned as yet.
    For the first time ever my fuel gauge has not dropped fast as well. I am happy with the open road performance, but concerned that I may be running too lean. How do I confirm this?
    Also what would be the solution to the hesitation from standstill?
    Would appreciate any advice, thanks.

  6. #21
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    .. try 49P rods if you can get them. Make sure they are EARLY design, later are different length with a different stepped shoulder)
    (good match for 71 jets those)

    float should be 11mm ... DOWN from the top of the casting (measured at the toe end)

    hesitation can be a few things... fuel level, APT piston wrong (+what power spring do you have?)
    but generally, accel pump not doing its job (have you renewed this?) or sometimes a mild vac leak
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  7. #22
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    Quote Originally Posted by Smitty2 View Post
    .. try 49P rods if you can get them. Make sure they are EARLY design, later are different length with a different stepped shoulder)
    (good match for 71 jets those)

    float should be 11mm ... DOWN from the top of the casting (measured at the toe end)

    hesitation can be a few things... fuel level, APT piston wrong (+what power spring do you have?)
    but generally, accel pump not doing its job (have you renewed this?) or sometimes a mild vac leak
    Unfortunately in South Africa not easy to get parts for these carbs. The 71 and 45B was what was originally in this carb. Would you say that this is the wrong combination?

    My carb is the early ones which does not have the APT adjustment. Spring for power piston is original from the carb so can't tell you that info.

    I am going to open up the carb and clean out all the passages and check the pump cup, hopefully its still good. Its a relatively new pump from Quadrajet Power so should still be in good condition I hope.

    My biggest concern is the jet and rod combination. My only alternative is to use the 76 jets which I believe is too big for my application. Was hoping you could confirm what the guys in Oz are using for stock 308 application for normal driving and economy.

  8. #23
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    Cliff Ruggles QJ book recommends 1/4" float level for all QJs.

  9. #24
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    Quote Originally Posted by GtoGeoff View Post
    Cliff Ruggles QJ book recommends 1/4" float level for all QJs.
    Okay, then I will raise the level to 6mm, which is close to the 1/4'

    What has experience been with such a high float level? Any seepage or wetness on the airhorn gasket?

  10. #25
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    Would anyone have the jet and primary rod sizes for the Holden Monaro HT from factory. My carb number is the same as what was used on these vehicles but cannot find any details for a baseline of the internal parts.

  11. #26
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    Cliff Ruggles QJ book recommends 1/4" float level for all QJs.
    Neither GM Rochester Division (who made Quaddies), GM Holden nor Doug Roe
    advocate that.... *

    GM Rochester and GM Holden state ..... for all 4MV - 11 mm ..or 0.46" is the correct float level
    using the factory float.

    Doug Roe advocates changing the float level depending on the needle and seat used!

    Doug has several tables in his books showing for early, late and 4MCE Quaddies
    what he reckons the levels should be for each type of needle and seat

    Use the 135 hi flo needle and seat, the float level on an early Quaddie should be 0.39"
    but is different again on a late model with APT.

    I use the GM setting on the Quaddies I build or reco.... with the factory float of course


    * I have no quarrel with Cliff, there is a large box of bits from him on its way to me!
    but somethings he states don't always work. You have to 'tune' a Quaddie to suit
    the engine it is bolted to ... what works on a 253 Holden engine does not
    work on a 455 Cadillac
    Last edited by Smitty2; 28-01-2021 at 09:02 PM.
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  12. #27
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    I set the float level as per the GMH factory manual at 11mm.

    For what it’s worth I’ve also watched a quaddy guru set the float level and he didn’t use any tools. When I asked he said it was a couple of whiskers under half an inch.

    I later, for my own edification, checked, and it was damn near exactly the factory spec.

  13. #28
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    So I just looked at the packaging list from Quadrajet Power when I had purchased my kit in 2019, its a 0.13 high flow needle and seat.

  14. #29
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by kavesh View Post
    Would anyone have the jet and primary rod sizes for the Holden Monaro HT from factory. My carb number is the same as what was used on these vehicles but cannot find any details for a baseline of the internal parts.
    yes, they will be in the genuine service manual . I have a copy of the manual in the shed
    will dig it out and let you know.
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  15. #30
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by Horaldic View Post
    I set the float level as per the GMH factory manual at 11mm.

    For what it’s worth I’ve also watched a quaddy guru set the float level and he didn’t use any tools. When I asked he said it was a couple of whiskers under half an inch.

    I later, for my own edification, checked, and it was damn near exactly the factory spec.
    .. couple of whiskers under half an inch eh?
    haha.. pretty close 11mm = 0.46"

    I have both the genuine measuring tool (very handy if you DO NOT want to pull the carby down)
    and a steel rule... steel rule is my usual weapon of choice in setting the float height*

    *ps.. whenever you do this ALWAYS hold the needle in the seat (at the other end of the float arm )
    seen people trying to set the float level and all they are doing is lifting the needle out, not setting
    the float height! They then complain ....doh!
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