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  1. #16
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by Castiron355 View Post
    That’s Quaddies in nutshell really. No one knows WTF is going on! Hahaha!!

    speak for ya self ...
    but I do build/rebuild/mod my own coz you are right, no-one knows ( I know of only 2 others who build/mod them)


    oh ...and for the record, technically Quaddies use a vacuum demand secondary power system
    Last edited by Smitty2; 05-01-2019 at 10:21 PM.
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  2. #17
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by GtoGeoff View Post
    " Mechanical secondary carbs are opened by a direct link from the primaries, usually on a progressive basis so the secondary opening is delayed until the primaries have reached approximately 40* of opening." [/I]This definition fits ALL Carter/Edel 4bbls carbs, QJs & TQs.......................
    that is incorrect as it applies to GM Rochester Quadrajets (I cannot comment on the other brands)

    I suggest you read any of the genuine GM technical/maintenance publications on the Quadrajet,
    even Holden's 'Improved Performance' Engine Manual which covers the blue/black engine range
    and has a large section on the Quadrajets fitted to both 253 and 308 engines (GMH Service manual M38338)
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  3. #18
    Sure why not? 76lxhatch's Avatar
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    Quote Originally Posted by Castiron355 View Post
    That’s Quaddies in nutshell really. No one knows WTF is going on! Hahaha!!
    A sad state of affairs, people seem to be unwilling to work with something that gives a bit more control and instead go for the extremely simple option. We're seeing the same thing with EFI now too, the massive advantage of electronics is the extra control you can gain but consumers would rather have a blunt instrument that forgoes all this, negating all the benefits.

  4. #19
    Not the Kingswood! hq308's Avatar
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    The problem is to get ďa bit more controlĒ usually comes at a cost. In the case of a Quadrajet that cost is considerably high in a lot of cases as very few people (me included) know how to tune them and/or where to get tuning supplies. The only option for most people is to find someone who has this knowledge and pay a premium for it. And thatís before you consider the availability of usable Quadrajet cores. On the flip side the average guy can grab a Holley and get it running close enough and spares are easy enough for most people to access.

  5. #20
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    EH179,

    Dork/dope/moron it seems you cannot read either. I gave you a quote from a carb engineer about how the secondary throttle blades [ sometimes called valves ] function.

    Here is another quote from Doug Roe's QJ book. DR was a GM engineer who worked on QJ design. Once you learn to read, he says this on p. 50, "The primary throttle lever opens the secondary throttle valves with it's connecting connecting linkage to the secondary throttle shaft lever." Your denials don't change facts! The sec t/blades & shaft of a vacuum secondary carb have NO MECHANICAL CONNECTION to the primary blades/shaft. Venturi vacuum opens the sec blades. That is the difference between a mech sec carb & a vac sec carb.


    To other, more enlightened members.

    If you look at the air valve of any of these types of carbs, you will notice large gaps between the AV & the carb body. Some QJs even had slots in the AV to help pull fuel from the sec starter cct. They are designed to allow air flow past the AV when it is at rest. As Doug Roe says: " Air flow through the secondary bores creates a low pressure beneath the AV..."
    Obviously if the AV was a tight fit in the body [ like the t/blades are ] there would be no airflow to start the AV opening procedure.

    A vac sec carb operates completely differently.....Vacuum acting on a diaphragm opens the sec throttle blades. The sec blades at WOT may never reach the fully open position depending on the control spring tension, unlike a mech sec carb..... Totally different designs.

    A little known fact. Carter tried a vac sec version of the AFB in the late 1950s. They are very rare, I have one. The design was quickly abandoned, presumably because the standard AFB worked better...

  6. #21
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    That is true. I did a tonne of reading on the quaddies. Their operation is very good and was really keen to dial one in. But as HQ said, itís not a matter of going to the local speed shop to pick up some parts.
    But as you say about EFI, itís the same as buying a Ultra XP and throwing it on. Itíll be close, but what it really has to offer is often overlooked.

  7. #22
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    I'll vote for the new Edelbrock AVS2 500CFM carb - the way it atomises fuel through its annular boosters, you'll probably see a minor gain in torque down low from that.

    With the FiTech EFI issues - you will have fuel distribution issues with a dual plane manifold and most throttle body injection style systems - they should be used with single plane manifolds and I remember seeing on their website a while ago that the FiTech system specifically mentions it shouldn't be used with a dual plane manifold, but I can't find the link at the moment, did it have starting issues?

    Engine masters had the same issue with another TBI EFI kit with a dual plane manifold.

    Do you still have this kit? It would trump any carb in regards to driveability and fuel economy if its running correctly.
    Last edited by Daymoe; 06-01-2019 at 12:51 PM.

  8. #23
    casual poster JaseQ314's Avatar
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    I should have bought more popcorn .

  9. #24
    Do you ever leave? EH179's Avatar
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    GtoGeoff

    You've been here 2 months and 20 posts in and name calling already...champion.

    Noticed you didn't respond to the Moderator of the forum with the same vigour, when he said you were incorrect?

    Go hard!

  10. #25
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    Quote Originally Posted by JaseQ314 View Post
    I should have bought more popcorn .
    Lolly gobble bliss bombs are the go !!

  11. #26
    been here .......too long Smitty2's Avatar
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    ... I am not biting (although I could)

    but just some more info to back up my previous posts on this thread
    and also correct info being posted that is wrong

    I took a spare Quaddie throttle body ('course everyone has one of those )
    and took some pics this arvo

    so below -
    a)... Quaddie as it would be at idle (Both primary and secondary throttles closed)

    b)...as it is with primarys about 85-90% open
    (NOTE ...the Secondary throttle blades, have NOT OPENED AT ALL!)

    It has been stated - the secondary opening is delayed until the primaries have reached approximately 40* of opening."
    This definition fits ALL Carter/Edel 4bbls carbs, QJs


    Pic b) .... is the important one, it clearly shows what actually happens


    c).. WOT on both power systems




    a)



    b)



    c)



    These are standard Quadrajet settings, as per what the factory setups were
    but if you know what you are doing, these can be adjusted to gain better fuel
    economy or better performance (sorry not both though )

    But of course, as per my previous post, if the secondary airvalves have not been
    opened by vacuum, the secondary throttle blades do zip nada. I should also state
    that these (secondary airvalves) have a vacuum break pull-off to control their opening
    Last edited by Smitty2; 06-01-2019 at 08:01 PM.
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  12. #27
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    Youíre such a nerd Smitty.👌

  13. #28
    Not the Kingswood! hq308's Avatar
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    Quote Originally Posted by Daymoe View Post

    With the FiTech EFI issues - you will have fuel distribution issues with a dual plane manifold and most throttle body injection style systems - they should be used with single plane manifolds and I remember seeing on their website a while ago that the FiTech system specifically mentions it shouldn't be used with a dual plane manifold, but I can't find the link at the moment, did it have starting issues?

    Engine masters had the same issue with another TBI EFI kit with a dual plane manifold.
    .
    Fitech TBIs work fine with a dual plane manifold. Fuel distribution for the most part is the same as a carb.


  14. #29
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    They do look the goods. Nice throttle linkage setup.

  15. #30
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    looking at that pic it looks more like a single plane than a traditional dual the Holden 955 for example has runners that T piece effectively bouncing off a wall which could cause fuel to "fall out" of atomization HDT even cut these in half to add a separator this was the "Bathurst" intake lol

    the above pic seems to have designed most of that out

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