Downleg Annular

[mike laws]

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[GTO Geoff]

Smaller diam, more speed. That is my interpretation also. And how the primaries in a QJ or TQ carb work. The extra booster ring in these effectively makes the area smaller by taking up more space. Result is a more sensitive metering system.

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[rgalajda]

Some measurements. Could be off by a few thousands.

3310-1 780 cfm downleg booster
.380 ID at the minor
.450 length
.620 OD
These dimensions seem to be consistent on newer models. Even a recent quick fuel 780 these dimensions were very close.

3310-2 750 cfm straight booster
.448 ID at the minor
.720 length
.627 OD
These boosters have a bar , so can't really be compared to down leg if looking at inside dimensions to compare flow. These dimensions seem to be consistent no matter what cfm holley carb .

As you can see your Race Demon down leg booster had a larger minor diameter of .430 compared to Holley down leg booster.

Autolite 4100 480 cfm Stepped Annular booster 1965
.530 ID at the minor
.993 length
.740 OD

Ford 4180 600 cfm holley Annular booster 1985
.620 ID at the minor
.740 length
.890 OD

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[Nick_nl]

How to these compare to regular down leg boosters?

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