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Old 07-07-2005, 07:29 PM
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Annular boosters - the real deal or marketing hype?

I recently read an article in Car Craft magazine about the comparison between annular boosters and downleg boosters in Demon carburetors.

Apparently, annular boosters generate a higher signal strength than the downleg boosters, allowing the use of larger carburetors and/or larger cams while still retaining good metering stability. This higher signal strength however requires smaller jetting than an otherwise identical downleg booster carb.

Annular boosters promote better atomization of fuel because they have many holes for the fuel to flow from, rather than just one big one like in the downleg boosters. This promotes better throttle response, fuel economy, and much better mixture distribution, especially at lower engine speeds.

The main tradeoff with annular boosters is that they are a bigger obstruction to airflow than the downleg boosters, thus lowering the effective cfm of the carb, all other variables being equal.

So, taking this load of information into a test of a hopped up LS1 with two 750 demon test units, Car Craft found that the downleg booster carb flowed an average of 19 cfm more throughout the RPM range, and as much as 65 cfm on the top end. However, the annular booster made an average of 7 more HP and 20 more ft-lbs, and as much as 96 more ft-lbs at 1800 RPM, even though it flowed less air. Their explanation was that the better quality mixture from the annular boosters accounted for the huge power increases. Keep in mind they tested a 500+ HP engine at wide open throttle from 1800 RPM up to 6700 RPM.

While this information gets me wide-eyed about annular boosters, I know better than to take results from a magazine at face value, for obvious reasons.

I thought I would summon the wisdom of this forum to validate the findings of this article. If anyone can vouch for the improved performance of annular boosters from their own experience, please share it with us.

I welcome your thoughts....
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Old 07-07-2005, 08:01 PM
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My personal experience was improved response guaranteed and possibly decreased top end. I'm not sure about the top end fall off, if it was there at all it was well worth the trade, and I'm a RPM type of person.

If Ford did 2 things right, this style of booster was one of them.
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Old 07-07-2005, 08:44 PM
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no hype, it's true
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Old 07-07-2005, 08:50 PM
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Annular boosters

The smallest Holley with annular boosters is the 750 cfm. So its not really suitable for any street car less than a 383. They are designed to work with single plane manifolds such as the Torker II or the Victor Jr. They are not recommemded for the Perf, Perf/RPM, or RPM Airgap.
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Old 07-07-2005, 10:43 PM
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Quote:
Originally Posted by bracketeer
The smallest Holley with annular boosters is the 750 cfm. So its not really suitable for any street car less than a 383. They are designed to work with single plane manifolds such as the Torker II or the Victor Jr. They are not recommemded for the Perf, Perf/RPM, or RPM Airgap.
Hmmm... could you please explain why they are not suitable for the dual plane intakes? I never realized this before...

I was also under the impression it is acceptable to move up one size of carb when you go to annular boosters, is this true?
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Old 07-07-2005, 11:20 PM
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no expert in that area

The info I gave you was what Holley tech line told me when I was hunting down a carb for my new 400sb.
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Old 07-08-2005, 10:38 AM
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Annular Vs. Downleg Boosters.

When it comes to annular vs. downleg boosters, there is not a clear right or wrong. Itís a matter of whatís going to work best on the application. There are Proís and Conís to both sides. An Annular booster can give you better atomization on an engine, which can result in better torque, HP, and acceleration. They can also allow you to get away with some components that may be too big for the application. Since the carburetor is generally the last thing that gets bolted onto the engine it has to make up for or compensate for a multitude of sins or mismatched components beneath it. If the cam is a little big, or cylinder heads, or not enough compression, etc. these things need to be taken into consideration. There is not a clear cut one is better than another, it would be much easier than, only having to offer one part. Itís more a matter of giving additional options to help fine tune, or tailor the application. On an engine where a 650 may be a touch small, but a 750 is going to be too large, a 750 with annular boosters may be a great option. Bottom line you need to go over your entire combination with your carburetor builder to determine which one of their carburetors is going to work best on your specific combination.
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Old 07-08-2005, 05:49 PM
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I keep mentioning the 4010. The jets face up, along with the powervalves. That way they don't get uncovered. There is only one gasket and it is above fuel level. It eliminates the possiblity of bad leaks, warped blocks, etc.

A 750 annular would work fine on a 350.

The 4010s were recommended for use on dual plane intakes as well.
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Old 07-08-2005, 07:39 PM
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The latest Car Craft has a comparo article on this very subject. I haven't had a chance to read it yet, but I figured I would throw out a heads up.
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Old 07-08-2005, 07:56 PM
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yes, this was the article that I was referring to when I started this post...
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Old 07-08-2005, 10:12 PM
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Yeah just noticed that. Sorry, it's an off night for me I guess.
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Old 11-15-2009, 08:13 PM
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what if i have a 194cid engine with a mild cam, headers Holley 500 cfm and dual exhaust. this is on a 66 nova. Will i benefit from annulars? I will not ever be racing,strictly cruise and mileage.
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Old 11-15-2009, 09:19 PM
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4 year old thread here. Beneficial booster for a warmed up 194? Simple, stick a Quadrajet on it.
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Old 11-15-2009, 11:40 PM
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Quote:
Originally Posted by sc2dave
what if i have a 194cid engine with a mild cam, headers Holley 500 cfm and dual exhaust. this is on a 66 nova. Will i benefit from annulars? I will not ever be racing,strictly cruise and mileage.
The basic rule of thumb is annular boosters will respond to a weaker signal than standard or down leg boosters, at the cost of some flow potential. They may be a benefit to you, but your CFM requirements are so low, I doubt there is a properly sized annular booster carb available.

A 390 CFM Holley comes to mind.

While a Q-jet could be made to work, all you need is the primary side of a Q-jet. This is the Rochester Duo-jet. It was a non-feedback 2-bbl used up until '80 on GM vehicles ('81- up Duo-jets are electronic). One of these could be used, but be aware that it has a bastard mounting flange compared to other 2-bbl.'s.

Another option is a non feedback Vari-jet. It's a staged 2-bbl. This acts like a single venturi carb w/a secondary barrel that opens at higher throttle angles. Has about 350 CFM, IIRC.

If it were me, I think I'd be looking for a dual 2-bbl. intake from Clifford, etc. Using progressive linkage, this would run AND look good!
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Old 11-16-2009, 07:12 AM
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Good idea Cobalt, two Dualjets on one would look cool.
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