The Edelbrock 1906 carburetor is a high-performance replacement for Q-Jet applications in non-computer-controlled Chevrolet and GMC V8 engines, spanning from 1966 to 1989. Designed for ease of installation and compatibility with both original and aftermarket intake manifolds, this carburetor offers a 650 CFM airflow rating and an electric choke system for improved cold-start performance. This guide provides a detailed, step-by-step explanation of the installation process, idle mixture adjustment, and choke linkage setup, based entirely on official documentation and specifications provided by Edelbrock.
Overview of the Edelbrock 1906 Carburetor
The Edelbrock 1906 is part of the Performer Replacement Series, specifically tailored for Q-Jet applications. It is a 4-barrel carburetor with a primary bore of 1.44 inches and a secondary bore of 1.75 inches, offering efficient airflow for a wide range of engine conditions. The unit features a satin finish and an electric choke system, making it suitable for both street and performance applications. It is compatible with both small- and big-block Chevrolet engines and includes all necessary gaskets, seals, and mounting hardware for direct installation.
Key specifications for the Edelbrock 1906 include:
- CFM Rating: 650 CFM
- Barrel Configuration: 4-barrel
- Primary Bore: 1.44 inches
- Secondary Bore: 1.75 inches
- Choke Type: Electric
- Material: Aluminum
- Mounting Flange Type: Square
- Vacuum Ports: Multiple ports for various engine systems
- Warranty: 12 months
These features make the Edelbrock 1906 a versatile and durable option for vehicle owners looking to enhance their engine's performance while maintaining compatibility with existing components.
Pre-Installation Preparation
Before beginning the installation process, it is essential to gather all necessary tools and materials and ensure a clean, organized workspace. The following steps outline the preparation phase:
Compare Old and New Carburetors: Place the original carburetor and the Edelbrock 1906 side by side. Transfer any necessary accessories, such as linkage brackets or vacuum ports, from the old unit to the new one. This ensures that the new carburetor functions as intended without requiring additional modifications.
Inspect Mounting Components: Check the intake manifold for any residue or debris. If necessary, clean the manifold with a degreaser and a soft cloth. This helps ensure a proper seal between the carburetor and the manifold.
Prepare Gasket and Mounting Hardware: Install a new mounting gasket between the carburetor and the intake manifold. Do not use any cement, glue, or liquid gasket, as these can compromise the integrity of the seal or damage the carburetor base.
Gather Tools: Have a short box-end wrench, a tubing wrench, and a manifold vacuum gauge (if available) on hand. These tools will be necessary for tightening bolts and adjusting the idle mixture.
Installing the Edelbrock 1906 Carburetor
The installation process involves several key steps to ensure the carburetor is securely mounted and properly connected to the fuel system and engine components. Follow these instructions carefully to avoid damage to the carburetor or engine.
Mount the Carburetor: Carefully place the Edelbrock 1906 onto the mounting gasket, ensuring that all ports and linkage points align correctly. Replace all mounting bolts, nuts, and washers. Begin tightening the bolts by hand, using even increments and alternating between diagonally opposed bolts to prevent warping or breakage. Use stock mounting bolts or the Edelbrock Q-Jet Bolt Kit #1925 for optimal performance.
Install the Fuel Filter and Hoses: For models with externally mounted fuel filters, install a new fuel filter. Start the threads by hand to avoid cross-threading or stripping. Replace any old or cracked hoses with new ones designed for fuel use. Hook up the fuel line to the fuel filter, again ensuring that the threads are properly aligned before tightening.
Tighten the Fuel Line: When tightening the fuel line, use two wrenches—one to hold the fitting on the carburetor and the second to turn the fuel line fitting. A tubing wrench should be used to prevent rounding the tube fitting nut. This step is crucial to prevent fuel leaks, which can pose a serious fire hazard.
Reconnect Throttle Linkage and Accessories: Reconnect the throttle linkage, wires, and hoses to the carburetor. The Edelbrock 1906 may have additional vacuum ports compared to the original carburetor; ensure that unused ports are capped to prevent vacuum leaks.
Install the Air Cleaner: Reinstall the air cleaner, making sure not to over-tighten the mounting nut to avoid damaging the carburetor.
Check for Binding: With the engine off, manually open and close the throttle to check for any binding or sticking. Ensure that the throttle moves smoothly from idle to wide open throttle. Any resistance or hang-up could lead to throttle stick issues, compromising engine performance.
Reconnect the Battery: Reconnect the negative battery cable to the battery to restore power to the vehicle.
Choke Linkage Installation
The Edelbrock 1906 features an electric choke system, which is designed to provide consistent performance during cold starts. Proper installation of the choke linkage is essential for optimal operation.
Wire the Electric Choke: The 1906 requires a 12-volt lead that is only hot when the ignition is on. Ensure that the wiring is properly connected and insulated to prevent short circuits or electrical interference.
Use Appropriate Choke Kits: Depending on the engine type and manifold configuration, Edelbrock offers specific choke linkage kits for the 1906. For small-block Chevy Performers with divorced choke carbs, use Choke Kit #1931. For big-block Chevy Performers with divorced choke carbs, use Choke Kit #1935. These kits ensure proper alignment and operation of the choke linkage.
Install the Choke Housing: If the original choke housing is not being reused, install the new housing provided with the choke kit. This housing helps retain the choke rod in the coil and ensures smooth operation.
Adjust the Choke Pull-Down: The choke pull-down should be adjusted so that the choke plate opens gradually as the engine warms up. This prevents sudden enrichment of the fuel mixture and ensures smooth idle performance.
Test the Choke Operation: Once the choke is installed, test its operation by starting the engine cold. The choke should engage automatically, and the engine should idle smoothly until the choke disengages as the engine warms up.
Idle Mixture Adjustment
Proper adjustment of the idle mixture is critical for optimal engine performance and emissions control. The Edelbrock 1906 uses conventional idle mixture screws (IMS) to regulate the air-fuel ratio at idle. Follow these steps to adjust the idle mixture:
Warm the Engine: Fully warm the engine and ensure that the choke is fully open. This ensures that the adjustment is made under normal operating conditions.
Install the Air Cleaner: Reinstall the air cleaner to provide a stable air supply during the adjustment process.
Adjust the Air Screw: Use the air screw to set the desired idle speed. This screw controls the opening of the primary throttles and should be adjusted to achieve a smooth, steady idle.
Adjust the Idle Mixture Screws: Begin by adjusting the IMS on one side of the carburetor to achieve the maximum possible RPM or vacuum (if using a manifold vacuum gauge). Do not over-lean the mixture, as this can cause engine stalling or poor performance.
Re-adjust Idle Speed: If the adjustment in step 4 caused the idle speed to change by more than 40 RPM, re-adjust the idle speed using the air screw.
Adjust the Opposite Side: Repeat the adjustment on the opposite side of the carburetor to achieve maximum RPM or vacuum. This ensures that both sides of the carburetor are balanced.
Fine-Tune the Mixture: Carefully trim each IMS to again achieve the maximum idle RPM or vacuum. Then, slightly lean the mixture by reducing the RPM by 20. This provides a lean-best idle setting, which optimizes performance without causing emissions issues or spark plug fouling.
Cap Unused Mixture Screws: Emission-legal carburetors, such as the 1903, 1904, and 1906 models, are supplied with tamper-resistant protective metal caps for the idle mixture screw wells. These should be installed after completing the final adjustments to prevent unauthorized tampering.
Special Considerations for EGR Applications
Some vehicles equipped with EGR (Exhaust Gas Recirculation) systems may experience a flat spot during off-idle acceleration after installing the Edelbrock 1906. This is due to differences in the location of the EGR vacuum port compared to the original carburetor. To address this issue:
Test for Flat Spot: If a flat spot is noticed after installation, temporarily remove and plug the vacuum line to the EGR valve. If the flat spot disappears, it indicates that a vacuum delay valve is needed.
Install a Vacuum Delay Valve: Purchase a GM vacuum delay valve (part number 14020691) and install it in the vacuum line between the carburetor and the EGR valve. This valve delays the opening of the EGR valve, allowing the carburetor to transition smoothly through the off-idle phase.
Verify Performance: Once the delay valve is installed, test the vehicle for smooth off-idle acceleration and overall performance. The EGR system should now operate normally without affecting engine response.
Post-Installation Testing and Troubleshooting
After completing the installation and adjustments, it is essential to test the carburetor for proper operation and to identify any potential issues.
Check for Fuel Leaks: During the initial start-up, inspect the carburetor and fuel lines for any signs of leakage. If a leak is detected, stop the engine immediately and repair the issue before continuing. Fuel leaks can lead to engine fires and serious injury.
Monitor Idle Quality: Observe the engine's idle quality after the carburetor is installed. A smooth, steady idle indicates that the mixture and speed adjustments are correct. If the engine runs rough or stalls, recheck the idle mixture and speed settings.
Test Acceleration and Deceleration: Take the vehicle for a short test drive to evaluate acceleration, deceleration, and overall performance. The Edelbrock 1906 should provide a noticeable improvement in throttle response and engine performance compared to the original carburetor.
Address Any Issues: If the vehicle exhibits poor performance, hesitation, or rough idle, refer back to the installation and adjustment steps to identify potential causes. Common issues include improper idle mixture settings, incorrect choke adjustment, or vacuum leaks.
Maintenance and Warranty Information
The Edelbrock 1906 comes with a 12-month warranty, covering defects in materials and workmanship. It is important to note that warranty service must be performed by Edelbrock or an authorized service center, as retailers are not authorized to handle warranty claims. If any issues arise during installation or operation, contact Edelbrock's Technical Hotline at 1-800-416-8628 for assistance.
To maintain the performance and longevity of the carburetor, regular maintenance is recommended. This includes cleaning the carburetor periodically, inspecting fuel lines for cracks or wear, and ensuring that all vacuum ports and connections are secure. If the vehicle is used in harsh or extreme conditions, consider using high-quality fuel and oil to prevent clogging and wear.
Conclusion
The Edelbrock 1906 carburetor is a reliable and high-performance replacement for Q-Jet applications in Chevrolet and GMC V8 engines. With a 650 CFM rating and an electric choke system, it offers improved cold-start performance and consistent idle quality. Proper installation and adjustment are essential for optimal performance, and following the manufacturer’s guidelines ensures that the carburetor functions as intended. By carefully following the steps outlined in this guide, users can confidently install and tune the Edelbrock 1906 to enhance their vehicle's performance and reliability.