The Edelbrock AVS2 (Air Valve Secondary) carburetor is a high-performance solution designed for classic and modern engines, offering improved fuel efficiency and throttle response. This article provides a detailed exploration of the AVS2's features, installation considerations, and technical recommendations based on official installation guides, FAQs, and performance testing data from Edelbrock. The information presented is derived solely from the manufacturer's documentation and is intended to assist U.S. consumers, DIY enthusiasts, and automotive professionals in understanding the AVS2 carburetor and its integration into various engine setups.
Overview of the Edelbrock AVS2 Carburetor
The Edelbrock AVS2 carburetor is part of a broader line of performance carburetors designed for both street and racing applications. The AVS2 model is available in three primary flow ratings: 500, 650, and 800 cubic feet per minute (CFM). These variations allow for compatibility with a wide range of engine sizes and power outputs, from small-displacement engines to high-horsepower setups. The AVS2 utilizes a mechanical secondary system with an air valve that opens based on air velocity, ensuring smooth throttle response and improved fuel delivery under load.
One of the key features of the AVS2 is its annular boosters, which enhance low-speed efficiency by requiring less throttle opening to achieve the same level of acceleration. This design allows for a more responsive engine feel, particularly during light load conditions, without the need for a secondary accelerator pump. The absence of a secondary pump simplifies the system and reduces potential points of failure, making the AVS2 a reliable option for both street-driven and performance-oriented vehicles.
The AVS2 is calibrated and factory flow-tested for immediate use, with no adjustments required for basic installation. However, for optimal performance, users are advised to consult the accompanying Owner's Manual for tuning procedures and operational theory. It is also important to note that the AVS2 is not intended for use in computer-controlled applications, such as certain 1981 and later GM vehicles with Q-Jet carburetors or Ford vehicles with automatic overdrive (AOD) transmissions.
Installation Considerations for the AVS2
Proper installation of the Edelbrock AVS2 is critical to ensuring both performance and longevity. The following sections outline key installation considerations, including recommended tools, torque specifications, and potential issues to avoid.
Pre-Installation Checklist
Before beginning the installation process, users are advised to review the following:
- Familiarity with Vehicle Systems: Installation should be performed by someone with experience in automotive systems. If the installer is not confident in their abilities, it is recommended to consult a qualified mechanic.
- Tool Requirements: Most installations can be completed with standard hand tools. The installation guide lists necessary tools, including a torque wrench, wire stripping tools, and a box-end wrench for NPT fittings.
- Compatibility Check: Ensure the AVS2 is compatible with the engine and intake manifold. For example, some Edelbrock intake manifolds require the use of a #2732 spacer for proper fitment.
Mounting the Carburetor
The AVS2 should be mounted on an intake manifold using a gasket kit and appropriate hardware. The intake manifold must be clean and free of debris to ensure a proper seal. Edelbrock recommends using a ¼-inch bead of silicone in place of traditional cork or rubber end seals to prevent leaks. If silicone is used, both the block and manifold surfaces must be cleaned with lacquer thinner and allowed to cure overnight before starting the engine.
When installing the carburetor, it is important to avoid using a torque wrench on NPT fittings. Instead, Teflon tape or paste should be applied to the first few threads of the fitting, and the fitting should be installed hand-tight or snugged with a box-end wrench. Over-tightening can damage the aluminum intake manifold and lead to leaks or cracks.
Electrical and Fuel System Integration
The AVS2 is designed to work with a variety of fuel delivery systems, including mechanical and electric fuel pumps. For electric fuel pump applications, Edelbrock offers the Quiet-Flo Electric Fuel Pump models #1790 (80 gph) and #1794 (120 gph). These pumps should be installed according to the manufacturer's instructions, ensuring proper voltage and wiring connections.
Wiring diagrams are typically included in the installation manual to guide users through the process. It is important to follow the recommended torque specs and wiring sequences to avoid electrical issues or performance degradation. If the installation involves EFI (Electronic Fuel Injection) components, the Edelbrock Pro-Flo EFI System may also be required. This system includes a comprehensive set of wiring, sensors, and control modules that integrate with the AVS2 for enhanced performance and control.
Troubleshooting and Maintenance
Despite the AVS2's robust design, users may encounter common issues during or after installation. The following are some frequently reported problems and recommended solutions based on Edelbrock's technical resources.
Air and Fuel Leaks
Air and fuel leaks can occur if the intake manifold or carburetor is not properly sealed. To prevent leaks, users should ensure that all surfaces are clean and free of debris before installation. The use of silicone as an end seal is highly recommended, and it must be allowed to cure for at least 24 hours before the engine is started.
If a leak is detected after installation, the intake manifold should be removed and inspected for cracks or warping. The gasket and seal surfaces should be cleaned with lacquer thinner and reinstalled with fresh silicone. In some cases, the leak may originate from the oil sending unit, which should be checked for proper sealing with thread sealant.
Throttle Response and Idle Issues
Improper idle adjustment can lead to poor engine performance and rough idling. The AVS2 should be adjusted according to the manufacturer's specifications, typically involving setting the idle mixture and idle speed. Users are advised to refer to the Owner's Manual for specific tuning procedures and recommended settings.
If the engine experiences hesitation or stalling under light load, it may be necessary to adjust the air valve secondary system. This involves checking the air valve's operation and ensuring it opens at the correct air velocity. The AVS2's mechanical secondary system does not use a secondary accelerator pump, so adjustments should focus on the air valve's responsiveness and fuel delivery characteristics.
Lubrication and Wear Protection
Flat tappet camshafts used in conjunction with the AVS2 require the use of an oil with enhanced zinc content to prevent wear. Edelbrock recommends its High Performance Zinc Additive #1074, which is designed to provide additional protection during cold starts and in vehicles that are not driven frequently. This additive should be mixed with up to 6 quarts of oil and can help extend engine life while improving horsepower and mileage.
Proper lifter preload is also essential for optimal performance. The recommended lifter preload varies depending on the camshaft and lifter kit used. For example, Performer plus camshaft and lifter kits require a ½ turn past zero lash, while Torker plus kits require a ¼ turn past zero lash. These settings ensure proper valve train geometry and reduce the risk of premature wear or valve train failure.
Performance and Tuning Considerations
The AVS2 is designed to deliver improved performance without the need for extensive tuning. However, users who are looking to maximize the carburetor's potential may benefit from some additional adjustments and modifications.
Fuel Jetting and Air Bleed Settings
While the AVS2 is calibrated for immediate use, advanced users may want to experiment with different fuel jetting and air bleed settings to optimize performance for their specific engine. These adjustments can affect fuel delivery at various engine speeds and loads, and should be made carefully using a vacuum gauge or other diagnostic tools.
It is important to note that the AVS2 does not feature a secondary accelerator pump, so fuel delivery during wide-open throttle is primarily controlled by the air valve and annular boosters. This design simplifies the system but requires careful attention to the air valve's operation and fuel delivery characteristics.
Clearance and Fitment
Clearance is another important consideration when installing the AVS2. The carburetor and intake manifold must fit within the available space in the engine bay, and users should check for potential obstructions such as the hood or air cleaner. A simple test using clay or foil balls can help identify clearance issues before final installation.
During the test, a few pieces of clay are placed on the air cleaner and the hood is closed gently. If an obstruction is felt, the hood should be opened to inspect the compressed clay and measure the clearance. This method helps ensure that the carburetor and air cleaner will fit without interference.
Conclusion
The Edelbrock AVS2 carburetor is a versatile and reliable option for a wide range of engine applications. With its annular boosters, mechanical secondary system, and factory-calibrated settings, the AVS2 offers improved low-speed efficiency and throttle response without the complexity of a secondary accelerator pump. Proper installation, including the use of silicone end seals, correct torque specifications, and compatibility checks, is essential to ensure both performance and longevity.
For users looking to maximize the AVS2's potential, additional tuning and modifications may be beneficial. However, these should be approached with caution and based on the manufacturer's recommendations. By following the installation guidelines and technical recommendations provided by Edelbrock, users can ensure a smooth and successful integration of the AVS2 into their vehicle.