Which one and why?
I understand the difference in them, design wise. But what are the performance differences? When will you use the annular boosters as opposed to the downleg booster? Which would work better on a road course or street? Which is better for big inch engines?
Jerry

This is one of the better articles on the subject:

http://www.hotrod.com/how-to/engine/116-0508-carburetor-showdown/

I am running annualars on my primaries on the hemi for crisp off idle response and downlegs on the secondary's for overall air flow in my Quickfuel 770's. Tim

I wanted to do the same but was told that I will get problems with fuel distribution between the different cylinders (fuel droplet size is different).

Everything I build gets an annular booster as long as the carb size isn't restrictive. With annular boosters it allows you to use a larger carb and still get as good or better atomization, better distribution of fuel. That means power. And with some modified booster inserts airflow loss can be kept to a minimum.

I run a 1050 Dominator with annulars on the street on my 440.Idle isnt great at times but it does have good response.Rocky

You need to work on the idle circuit then...........idle bleeds and ifr`s and then tweak the idle mixture screws to fine tune.........

We are testing two 4150 style Quickfuel 1050's on my 511. They are identical other than the boosters. I've had good luck with annular boosters.

Good info guys. Thanks for the link Andy.

Yes, that's a good article. This might be of interest.
http://www.hotrod.com/how-to/engine/0511phr-carburetor-boosters-tech/

I can see where that makes sense and even more so after reading the article.

I wouldn't believe that. Reason being is the need and how the engine reacts to the fuel at different engine speeds and loads. A fine mist for low speed and cruise conditions and bigger droplets of fuel for high load/speed (AKA - W.O.T.)

Since driving on the primary side is probably better with the angular booster and the WOT works best with bigger droplets, the combo of boosters are a good theory to try out.
Jetting is key to everything.

EVERYTHING being correct is the key............jetting is a good part of the fuel available and emulsion, angle channel size, booster type and outlet size, bleed size etc. all contribute to a "Clean n Mean" working carb............

Mark would you explain modified booster inserts please?

Thanks,
Don

i think he Mark was implying, if you use a booster insert like the red ones in the first post vs something like this fat holley annular booster, then you lose less of the cfm capability of the carb...

I like the response of the annular boosters, but they do lower the CFM rating of the carb (given same bore size.)