Performance you can depend on from a name you can trust...

Edelbrock engineers have made a great carburetor even better. The new and exciting Thunder Series AVS carbs are designed and calibrated to deliver optimum street performance in hundreds of applications--they are undeniably the most innovative and dependable street performance carburetors available today. AVS stands for Adjustable Valve Secondary, which means just that--you have the ability to adjust the secondaries with simple tools (no springs required).
You can use a late opening for heavy vehicles with higher gears or an early opening for light vehicles with lower gears. For unmatched street performance, combine these carburetors with Edelbrock Performer, Performer Air-Gap, Performer EPS, Performer RPM, RPM Air-Gap, or Torker II manifold and camshaft combinations.

Thunder Series AVS Highlights: All the same advantages of the Edelbrock Performer Series, such as factory-set float levels for infrequent adjustments, 2-step metering rods for independent tuning of cruise and power circuits, and the ability to change jets, adjust floats, or replace needles without draining fuel Qwik-Tune secondary air valve A sturdy 2-piece body with no power valves to blow and no gasket below the fuel level for leak-free operation CNC-machined and profiled front face delivers a smooth, custom look Tumble-polished or Endurashine finish Spring-loaded needles and seats for consistent fuel supply over rough terrain and side-mounted fuel chambers that are less likely to flood when a vehicle climbs hills (ideal for off-roading and the 4x4 environment) Optional single or dual inlet for total fuel plumbing flexibility Available in 500, 650, and 800cfm with either manual or electric choke

Edelbrock Carburetor Application Guide