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Holley Truck Avenger carb, detailed pics (m.j. this one is for you)

Discussion in 'The Garage' started by Twiz, Sep 25, 2002.

  1. Twiz

    Twiz 1/2 ton status

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    *Holley Truck Avenger carb*

    From what it looks like to me, it appears to be a "standard" Holley 650 carb with some modifications that are pretty dawg-awn cool!
    This shot (and the pics that follow it) clearly show the Annular Boosters. The restrictive (but better) primary booster design is probably why this carb is rated at 625 CFM and not 650. All-though I doubt the boosters restrict the air flow that much.

    Detailed pics of the "modified" Metering Block -vs- A Stock Block.
    Main Body to Metering Block
    Metering Block to Main Body
    Metering Block to Float Bowl



    Holley Truck Avenger carb album.
     
  2. Twiz

    Twiz 1/2 ton status

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  3. Twiz

    Twiz 1/2 ton status

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    The truck this carb came from was a '72 Blazer that was converted to a truck, makeing it a super-short bed truck.

    The owner described the problem as a "flat-spot" or "it falls on it's face" as throttle in-put is increased. Sounded like a Power-Valve problem - or something like it.
    After the owner tried several different P/Vs, Jets, Squiters and afew calls to Holley. The owner was about ready to throw in the towel.

    On the actual test drive (which should have been done first), it was obviouse that the problem was NOT load sensitve (I.E. Power Valve related) but throttle position sensitive. It would all-most stall just off idle.

    After removal and inspection of the carb, the problem was found:
    http://community.webshots.com/photo/50946675/51023425rLJzCy

    Holley replaced the carb under warranty within the day. The new replacement carb did not show the same problem, so I'm guessing it was just a fluke- mass-production tolerance thing and nothing more.


    Just the way goes sometimes.
     
  4. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    very nice /forums/images/icons/smile.gif how well does it work?
     
  5. m j

    m j 1/2 ton status

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    cool!
    and it didnt cost ya $400 to check it out, some other sucker fell for it and you got paid to play. lucky dog.
    thanks for sharing.

    I dont see, at first glance, any diffences in the metering block that look like they will prevent gravity from pulling fuel through the mains when climbing.
    did you?
    I will be studying those pic in more detail

    </font><blockquote><font class="small">In reply to:</font><hr />
    Exclusive New "No Trouble" metering block eliminates fuel spillover through the boosters at extreme angles. Flood-free operation up to 40 degrees while climbing and 30 degrees during side hill maneuvers and "nose down" descents. This allows you to off-road in confidence with out the annoying hesitations, stalling and flooding typically associated with carbs in an off road environment.


    [/ QUOTE ]
     
  6. Twiz

    Twiz 1/2 ton status

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    I didn't notice any mayjor changes with the Metering Blocks, mostly just minor differences that could be related to up-dates during the 650's long production run, or just adjustements that were needed due to the Booster change.
    That doesn't mean they arn't there, they could be hidden inside the blocks or something else.

    One thing that came to mind, but I didn't think to look at closely at the time is the fuel-level in the bowl.
    With the better booster design, it would/should pull harder on the jets, requireing less fuel pressure at the jet (I.E. the height of the fuel level above the jet changes the fuel pressure at the jet. I'm NOT talking about the over-all fuel pressure in the line.) If that is the case, then the fuel level in the bowl could be lowered and there-for raise the "spill-over" height.
     
  7. m j

    m j 1/2 ton status

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    sounds like you are stretching it a bit there. pressure at the jet? /forums/images/icons/tongue.gif
     
  8. Twiz

    Twiz 1/2 ton status

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    The weight of the fuel at the jet. (sorry)

    If you raise the fuel level, the carb will run slighly richer.
    If you lower it, it will run leaner.
     
  9. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I would think that the volume of fuel in the bowl would be negligable as far as "cylindrical height" over the jet raising fuel pressure. In english: The pressure at the jet with a bowl full of fuel vs. the pressure at the jet with the bowl almost empty would be negligable. Also if there is a higher vacuum signal below the jet, I would think that you would actually want the fuel in the bowl to be higher to prevent A.) fuel from running out, or B.) the jet creating a correolous (sp??) effect (think bathtub draining) in the fuel bowl drawing in air.
    Granted the jet meters the fuel (fuel flow rate), but it is rated under like conditions [Standard Temperature and Pressure(s) or STP] A jet that is sized to flow X amount of fuel with a weak vacuum signal below it, will flow X+ with a high vacuum signal below it. There is a point where it is physically impossible to flow more fuel (i.e. you can't just raise the vacuum signal and get more fuel through a certain size jet, but I don't think the "terminal vacuum" can be reached in the standard internal combustion engine. Do these things make sense, or am I just blowing smoke out of my butt /forums/images/icons/blush.gif /forums/images/icons/tongue.gif
     
  10. m j

    m j 1/2 ton status

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    well spoken smoke emission. /forums/images/icons/grin.gif
     
  11. m j

    m j 1/2 ton status

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    I dont buy the pressure theory, as the fuel is in an open vessel on both sides of the jet.
    raising fuel float level will have the fuel in the main well closer to the discharge nozzle
     
  12. Twiz

    Twiz 1/2 ton status

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    No, No, the other way around...Lowering the float will inturn, increase the "spill-over" hight.
    You said it yourself in another post:
    </font><blockquote><font class="small">In reply to:</font><hr />
    but they will not climb with the fuel being held in the stock location, to bandaid this you lower the float levels as much as possible

    [/ QUOTE ]
    Thats exactly what I've been tring to say all this time.

    I'm saying, that Holley might have been able to lower the fuel level setting in the bowl (-thus increaseing the "spill-over" height-) because the better boosters pull harder on the jet, so the jet doesn't need as much "help" from the weight of the fuel above the jet to begin working.
    I was just thinking "out-side the block", so to speak.

    It's a moot point, anyway. With a closer look at the sight-plug on the carb, it looks to be in the normal position to me, maybe even a bit higher than normal.

    I'm not going to say their adsvertizing claims aren't ligit', because I don't have enough evidence to say other-wise. I like the carb, and would bolt it on to just about anything.

    Still, I'm going to stick with the tried and true, for my "Wheelers". (Q-jet)
     
  13. Twiz

    Twiz 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    The pressure at the jet with a bowl full of fuel vs. the pressure at the jet with the bowl almost empty would be negligable

    [/ QUOTE ]

    True, to an extent. But remember, we're dealing with a "14 to 1" ratio (14 "pounds" of air to one "pound" of fuel - right?). Think about how much air is needed to match it to one "part" of fuel.
    If you increase or decrease the fuel, by even a slight amount, the air will need to be changed 14-times that amount, to maintain the same "14 to 1" ratio.

    Further-more:
    A slight change in elivation, say from sea-level (14.7psi) to the mountains (say, 13.7psi, guessing) makes a noticable change in performance, and thats changing the "high-end" of the ratio.



    Am I correct in my thinking?
    Is the ratio "14 to one", given as weight? I know it's said "14-parts of air to one part of fuel", but what is a "part"? Atomic weight? Mass? Or Volume?
    (I know I've read this somewhere, but I can't remember it right now)
     
  14. m j

    m j 1/2 ton status

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    the fuel is not under pressure IMO
    the weight at the jet means next to, if not, nothing as it is drawn from above the bowl level

    </font><blockquote><font class="small">In reply to:</font><hr />
    No, No, the other way around...Lowering the float will inturn, increase the "spill-over" hight.
    You said it yourself in another post:

    [/ QUOTE ]

    really? it would have been an error on my part if I stated increasing fuel level in the bowl was good for climbing.
    as soon as the main discharge is lower then the highest point of the fuel gravity wins and fuel flows down into the engine.
     
  15. 70~K5

    70~K5 1/2 ton status

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    you'd want to lower the front float and raise the rear one for hill climbing with a holley. When the nose of the truck is up the fuel in the front will flow to the rear of the float bowl. In the rear bowl the fuel will flow away from the jets. /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rotfl.gif
     
  16. Twiz

    Twiz 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    the fuel is not under pressure IMO
    the weight at the jet means next to, if not, nothing

    [/ QUOTE ]

    So, your saying the float level setting is just a random setting, dreamed up by the engineers?

    If so, then why is it set so acurately, to the 64ths of an inch in some cases. Why not "just slap it togather and go"?
    Hell...Why run such a large float-bowl at all? If the fuel level means "next to nothing", a small puddle of fuel for the jet to pull from would serve its purpose, as long as the needele and seat could flow enough to keep up with the demand.

    Why is the float bowl vented to the same "air" as the air-horn is exposed too?

    If air has pressure (14.7 at sea-level) than why is it so hard to acept that a 1.5" well of fuel, also holds a specific pressure?




    Or are you just messin' with me?
    /forums/images/graemlins/grin.gif
     
  17. m j

    m j 1/2 ton status

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    So, your saying the float level setting is just a random setting, dreamed up by the engineers? probably

    Hell...Why run such a large float-bowl at all? If the fuel level means "next to nothing", a small puddle of fuel for the jet to pull from would serve its purpose, as long as the needele and seat could flow enough to keep up with the demand. the needle and seat cannot keep up, I have seen the results in a nitrous'd 396 mudbogger

    Why is the float bowl vented to the same "air" as the air-horn is exposed too?cause it is clean and filtered?

    If air has pressure (14.7 at sea-level) than why is it so hard to acept that a 1.5" well of fuel, also holds a specific pressure
    I never said it didnt have a pressure. I said it means **** all in regards to what the engine sees.
    the pressure at the deepest point of the pacific has nothing to do with water splashing on the beach either.
    IF the fuel was being pressed through the jet by the cylindrical height theory then yes it would make a difference.
    as it is being drawn from above the level of fuel in the bowl I dont think it make a rats difference.
    all that I see is the distance from the wet fuel to the booster that the fuel must be drawn.
    seems I only get to reply to this roughly and hurried with no chance to spell out plainly what I mean.
    I keep assuming you will see what I am talking about.
    how about when you drink through a straw?
    does the Coke come to your mouth easier when the glass is full? or half full?
    now if there is a difference is it from the increased vertical distance you have to draw it or from the increased pressure at the straw inlet?
     
  18. Twiz

    Twiz 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I keep assuming you will see what I am talking about.
    how about when you drink through a straw?
    does the Coke come to your mouth easier when the glass is full? or half full?


    [/ QUOTE ]

    Excelent point. I do indeed see what you are saying, allways have, even more so when you put it in bold.

    A carb meters the air and fuel by a pressure difference. The weight of the fuel above the jet is part of the metering system.

    I swear, I'm not B.Sing you here....Got it?
     
  19. m j

    m j 1/2 ton status

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    the hieght of the fuel column is equal on both sides of the jet.
    so would this not = a zero gain
     
  20. Twiz

    Twiz 1/2 ton status

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    I hate you....
     

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