28 CHEVY HIGH PERFORMANCE II NOVEMBER 2019
Going Annular
Parts List
Description PN Source
Edelbrock AVS2 500-cfm, electric choke EDL-1901 Summit Racing
Edelbrock AVS2 500-cfm, manual choke EDL-1902 Summit Racing
Edelbrock AVS2 650-cfm, electric choke EDL-1906 Summit Racing
Edelbrock AVS2 650-cfm, manual choke EDL-1905 Summit Racing
Edelbrock AVS2 800-cfm, electric choke EDL-1913 Summit Racing
Edelbrock AVS2 800-cfm, manual choke EDL-1912 Summit Racing09 | Edelbrock’s latest
addition is an 800-cfm AVS2
carburetor for larger engines.08 | Setting the idle mixture is easy as both screws are located in the front. Edelbrock recommends having
the engine fully warm and connect a vacuum gauge to manifold vacuum. Carefully adjust one idle mixture
screw to obtain the highest manifold vacuum and rpm. If the idle speed increases more than 100 rpm,
reduce the idle speed and then adjust the second mixture screw for the highest engine speed. Then turn both
mixtures screws in (leaner) to see a 20 rpm drop. This is the best lean-idle setting.
rule of thumb is if you notice the
secondary opening—which some will
attempt to claim is actually good—the
spring tension is too loose. That “hit”
is really a minor hesitation.
One of the attractive tuning
points of the entire line of Edelbrock
carburetors is that the primary
metering side is both very easy to
adjust and offers the ability to make
very slight changes to the metering
circuit both to improve throttle
response and perhaps achieve
small gains in fuel mileage. All of
Edelbrock’s carburetors control the
primary fuel flow in the same manner,
using a primary metering jet that
includes a tapered metering rod.
The metering rod is controlled by a
piston that includes a small, calibrated
spring not much bigger than ball
point pen spring. With high manifold
vacuum, the vacuum pulls down
on the piston and compresses the
spring. This places the wide portion
of the tapered metering rod in the
primary jet, reducing the fuel flow. This
leans the air/fuel ratio mixture, which
can often lead to improved throttle
response and better mileage.
When the throttle is opened and
load increases, manifold vacuum
drops off and, at the proper time, the
spring will push up on the piston,
raising the metering rod so that
the smaller, tapered end of the rod
increases the flow area of the jet
and richens the air/fuel ratio. The
advantage of this system is that
the tuner now has two different
diameters of the metering rod—the
primary jet and the power valve spring
calibration—to use as tuning points.
This is in comparison to a traditional
carburetor with just a primary jet and
the power valve. If you are familiar with
Quadrajet carburetors, their primary
metering system is very similar.
Far better than the Q-jet, the
metering rod and power valve spring
are easily accessible on the top of
the Edelbrock carburetor by simply
loosening a couple of Torx-head
screws. Once loosened, the small
cover can be slid out of the way and
the metering rod and power valve
spring are immediately accessible.
This makes minor tuning changes
incredibly quick and easy.
This rather quick description
should illustrate that there are multiple
advantages to choosing the AVS2
carb for the typical, mild street engine
application. The AVS2 offers the
advantage of super-responsive throttle
action every time you hit the throttle.
That should be worth something. CHP