Keeping Things Simple With the New AVS 2 Carburetor From Edelbrock

By Todd Ryden – Photography by the Author

Modern technology has certainly crept into our world of hot rodding and performance. There are plenty of electronically controlled devices, from ignitions to gauges, transmissions, and, of course, fuel injection systems. In many cases, these make great updates to our Chevys, but sometimes keeping things simple is a welcome change.

One of the great debates over the last decade is that of going with modern EFI or sticking with the old technology of a carburetor. It seems that all the talk is about throttle bodies and port fuel injection these days, but we recently saw the updates Edelbrock made to their line of AVS series carburetors and we can tell you that the R&D on their tried-and-true carbs continues right alongside their EFI program.

When Edelbrock updated their AVS carburetor line, they started by refreshing their molds to give the new models great looks and precision. The carb housings are cast and assembled in Edelbrock’s Sanford, North Carolina, foundry.

They recently released the next generation of their carbs as the AVS 2 series, which has received a number of upgrades while keeping it affordable and easy to tune. In fact, they started with all-new tooling for the carb, which is cast and assembled in Sanford, North Carolina. You’ll quickly notice the details and crisp appearance of the fresh housing right away.

Another external update is an adjustable secondary air valve, which allows you to set the rate at which the secondary air valve opens compared to the original counterweighted flap design that was preset on some applications. This adjustment helps tune the transition to the secondaries as you roll from low rpm to wide-open throttle.

The major upgrade to the AVS 2 are the two primary annular flow boosters in the primaries. These rings feature eight small orifices that greatly improve the fuel discharge to improve atomization of the fuel.

A third, and the most significant upgrade, is in fuel delivery through the primary boosters. Rather than the typical ”down leg” booster that has been used for years, Edelbrock created an annular-flow booster, which produces a larger spray pattern through the venturi to improve the atomization of the fuel before entering the intake manifold. The new boosters feature eight equally spaced orifices that are fed from fuel circling around the entire booster, creating a spray pattern that is similar to a fuel injector.

The major upgrade to the AVS 2 are the two primary annular flow boosters in the primaries. These rings feature eight small orifices that greatly improve the fuel discharge to improve atomization of the fuel.

We found ourselves wanting to simplify things on our 1964 Chevelle and actually pulled off an old throttle body EFI system to try out the AVS 2. We’ve tested a lot of parts on this car and felt it was time to go back to basics. The EFI was nice to have for cold starts and for trips through the mountains, but sometimes simplicity trumps modern technology (along with the cost).

Our small-block is a pretty basic 350 with a hot cam, Performer intake, and a set of headers, so the 650-cfm AVS 2 was chosen in a satin finish. We went back to a mechanical pump and had to get a small linkage adapter to correct the TV cable geometry from the 200-4R transmission (Edelbrock PN 8026), but other than that, all of the linkages and lines hooked right up.

The rear port of the carb is a direct source of manifold vacuum, which is perfect for a power brake booster or for the PCV line. We already have a port directly into the manifold for our brake booster, so we installed a 90-degree fitting to route the PCV 3/8-inch line to the carb base.

With the engine fired up, we set the idle mixture screws and idle speed and headed out for a drive. Everything felt good right out of the box with no rich smell or rough idle, and the throttle response driving away from stop lights felt just fine—right how the older EFI system felt. One area we were concerned about was the ease of starting after sitting for a few days, but with a couple pumps of the throttle and a couple cranks, the engine came to life. We did fiddle with the choke flap to have it come off a little quicker, which is an easy adjustment and detailed in the thorough instructions included. With a few hours of driving time on the freshly carb’d Malibu, we feel pretty good about choosing a carb again, albeit a carb with modern updates!

After some much-needed cleanup on our intake, we installed the carb on the Edelbrock Performer manifold we’ve been using for years.
The AVS 2 has a fuel inlet on each back corner and we opted for the rear passenger side like most vehicle applications. An Edelbrock hardline (PN 8131) was used that cleanly routes under the choke assembly and forward to a supplied filter. Using a filter between the carb and pump is recommended.
The AVS 2 has a fuel inlet on each back corner and we opted for the rear passenger side like most vehicle applications. An Edelbrock hardline (PN 8131) was used that cleanly routes under the choke assembly and forward to a supplied filter. Using a filter between the carb and pump is recommended.
The port on the passenger side is known as ported or timed vacuum, which doesn’t come in until the throttle blades open. If you’re running vacuum advance on your distributor this is where to connect it. The driver-side port is manifold vacuum and served as a source for the transmission’s vacuum modulator (in our case, it’s for the vacuum control of the 200-R4 converter lockup).
When installing any carb (or throttle body) it is important to ensure that the shift linkage geometry is designed for your specific transmission. If running a 700-R4, 200-4R, or 4L60, an adapter will be required to connect to the transmission’s Throttle Valve (TV) cable. Edelbrock offers one as PN 8026 that easily bolts to their linkage. Without this simple $15 piece, you can hurt your transmission!
With the fuel line and vacuum lines connected along with a throttle return spring, it was time to crank over the carb and fire up the 350. It took a bit of cranking, but once the new filter and fuel bowls were filled with fresh fuel the engine roared to life and we scanned for any signs of leaks–all good!
As the engine warmed up to operating temperature, we adjusted the idle speed screw (near the throttle linkage) to get a baseline idle and then adjusted the air mixture screws. Start with one idle mixture screw by turning it fully in (lean) then back it out to obtain the highest idle speed. Then, do the same with the other screw and reset the idle speed screw.
As the engine warmed up to operating temperature, we adjusted the idle speed screw (near the throttle linkage) to get a baseline idle and then adjusted the air mixture screws. Start with one idle mixture screw by turning it fully in (lean) then back it out to obtain the highest idle speed. Then, do the same with the other screw and reset the idle speed screw.
Our model is equipped with an electric choke that can easily be adjusted to determine the amount of time the choke stays closed. The black cap will be rotated to the full lean (CCW) position and run the engine to its operating temperature. With the engine running, turn the cap clockwise until the choke valve starts to close then turn it one notch CCW (lean) and tighten the choke capscrews.
The secondary air flap is easy to adjust on the AVS2. This controls how quickly the flap opens to initiate the secondaries.

Sources:
Edelbrock
(888) 799-1135
edelbrock.com

Speedway Motors
(800) 979-0122
speedwaymotors.com

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