Down Leg vs. Annular Boosters
 

My old carbs had "downleg" boosters. Newer carbs offer a choice between downleg & annular boosters. It seems to me that the downleg boosters are a bit smaller and don't detract as much from the carbs CFM rating. Are there advantages to using "annular" boosters? :question:

I see you run a 406. Tell me more about your combo. I run what must be a similar set up, 406, Camaro, I had the best times with a box stock, rejeted 950HP. I tried a 830 annualar set up, ran good, but not as good as the 950HP. Tried a tricked out Biggs (borrowed), no better, no worse.

From what I understand annular boosters allow you to run a bigger CFM carb so that you can have it for the airflow up top and it maintains the lower end of the RPMs better.

Boosters pull fuel out of the main well via vacuum signal in the main bore. Boosters are actually a second venturi, and the smaller bore, coupled with lots of small holes around the ID (aka annular) let it react faster and more crisply in a carburetor that's "too big" per usual thinking.

Like the above two posts, if you have enough motor to require a 950, but that much carburetor doesn't work well (is mushy) at lower RPM levels, then a change to annular boosters will likely help.

Thanks guys! According to everything I've been reading on this topic, the annular boosters should offer a bit more throttle response than a down leg booster on the same size carb. While perhaps cutting down the CFM rating a little.

I'm in the middle of building a radical street motor (500+ cid) and a "Dominator" is just too close of a fit under the hood. They do make "down leg & annular" 4150 style carbs that flow up to 1050 cfm that do fit. I guess the annular boosters will help to make the motor a little more "streetable!" :D