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#1
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Annular Carb on the Street
What size/brand of annular carb do you run on the street and how do you like the throttle response?
Thanks |
#2
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On my 496 Cuda, I have a Holley 850 DP with annular boosters. Excellent throttle response.
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#3
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i ran a Holley #0-9381 830cfm w/annular boosters on my 440 / 4-spd.
i loved it. good throttle response (especially off-idle through mid-range) nice little bump in mileage (like i really care) annular boosters are physically larger (and therefore, more restrictive in the venturis), so you must consider this when determining the carb CFMs you need to feed your mill. i'm sure there's reasons why you wouldn't want an annular carb in some apps otherwise Holley wouldn't still be selling carbs with the downleg and straight boosters. can anybody else shed some light on this |
#4
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Some booster basics, as published in "Camaro Craft" magazine:
http://www.carcraft.com/techarticles...own/index.html |
#5
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In theory, the annular boosters give better throttle response on the street, but the downleg give a slightly higher top end power (but on a 500 horse engine I think we are only talking 10 hp or so), but I ain't no expert.
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#6
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8896 holley. I would say that the throttle response and such are not because of the booster style. Annular boosters are said to react to smaller signal changes than down leg style. I think for most people, the booster syle is not on the 10 most important features of the carburator list, and shouldn't dictate the choice.
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#7
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Quote:
But, if annular boosters react to smaller signal changes, then they are going to be more throttle responsive? |
#8
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Not necessarily according to my experience, I think other things act a bigger role in the throttle response thing, than the boosters reaction capability. It's not a night & day difference anyway, and both have their sides and purposes. I guess they would all be annular, if that weren't the case?
The biggest increase in responsiveness I have experienced was going from an annular booster carb to conventional, and that change was huge, like a completely different engine & car, but it surprisingly didn't affect 1/4 mile performance at all. The annnular carb was a regular holley, while the conventional was a Chuck Nuytten prepped pro street carb. |
#9
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Annular boosters have multiple holes (8-12 manuf pending) around the casting that allows smaller fuel dropplets to be interduced into each venturi. The downleg has one large hole.
The Annular booster reaches across the venturi opening taking up more space than the downleg so the maximum cfm rating is lowered. I have reach where some companies show a 35cfm drop and I know for a fact that the Quick Fuel annulars only have a 15cfm drop (750cfm annular is actually a 735cfm). An annular helps out on the bottom-mid range driving and the downleg is best for the top end driving range. But, when an annular is "properly" sized for a combo, it will have enough cfm rating for the top end and give better bottom-mid range driving too. They are the best of both worlds when properly sized. The annular will have smaller jetting than a downleg because the annular has a better reaction time and will pull more fuel thru the smaller jet than that of an equivelent downleg carb which results in more efficient fuel consumption during normal driving. The annular may cost more though. Thank you for the responses. |
#10
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The fuel has been mixed with air int eh emulsion tubes already before it reaches the boosters, so unless you have something wrong in there, you souldn't really have any "droplets" coming out of the boosters. The shape of the downleg booster mixes the fuel as well, if the carb is properly sized = enough velocity. Annular boosters tend to work better with less flow velocity, at part throttle etc. But again, the difference really isn't earth shaking as far as I've experienced.
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#11
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Dart,
Thank you for clarifying my response. I do not want to pass on the wrong information. |
#12
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isn't off lign throttle response controled mostly by the pump shot and the sqiurters??
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#13
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I just recieved my first annular carb. It is a Quick Fuel Super Street 750 (SS-750-AN) and I can't wait to test it in the Spring. I have three other downleg carbs that I have run on this motor, so I should be able to find out first hand how an annular reacts.
Is an annular carb tuned the same as a downleg version? I have read where the annular pulls more fuel thru smaller jets (this carb came stock with 68/82's) so I am curious if there are any tuning differences due to the booster design. Thanks |
#14
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Holley 4150 style 1,000 cfn pro-series vacuum secondary carb with annular boosters on the 451 stroker engine, and it is very responsive and very nice on the street too. Chassis dyno shows nice near flat A/F ratio a WOT.
With the 10" converter I can't say how it well it would respond below 2,500 rpm with a tight converter. |
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