Chevy High Performance – November 2019

26 CHEVY HIGH PERFORMANCE II NOVEMBER 2019

05 | Note that the AVS2 only uses annular boosters on the primary side of the

carburetor. They are much more effective at lower engine speeds and lower air

velocities, which is why they work best on the primary side. On the last of the

carbureted 5.0L Mustangs in 1985, Ford did exactly the same thing, placing

annular discharge boosters only on the primary side of the carburetor.

07 | If you want to experiment with the secondary air-valve door spring

adjustment, this is also easily accessed. Loosen the Torx locking screw and then

turn the straight blade screwdriver slot. Clockwise tightens the spring tension

and delays the opening while counterclockwise loosens the tension on the air-

valve door. Make very minor changes here to evaluate the effect.

06 | Minor primary side metering changes can be accomplished by loosening
the Torx head screw on top of the carb and removing the primary metering rod
and power valve spring. This does not require removing the carburetor lid unless
you need to change the primary or secondary jets.

Going Annular

04 | This is an annular booster removed from the carburetor. You can
see several of the smaller holes on the inside circumference of the booster.
Edelbrock has anodized the annular boosters red to make them easier to identify.

Annular boosters do such a great
job of creating a signal to draw fuel
into the airstream that the system
has to be drastically re-jetted to
compensate for this higher efficiency.
You will note on the AVS2 that only the

primary side of the carburetor uses

annular discharge boosters. That’s

because as the air velocity through the

carburetor increases, there is less of

a difference in performance between

these two boosters. By the time the

engine sees sufficient rpm to open

the secondaries, the velocity is high

enough that annular boosters offer no

significant benefit.

As a simple test to reveal part-

throttle driving time, try this little

03 | This is an illustration of how
an annular discharge booster works.
Instead of one large discharge port,
as with normal boosters, the annular
flows fuel from 12 smaller holes
located around the inside diameter
of the booster. This creates much
finer fuel droplets that burn more
efficiently.