Understanding the Holley Street Avenger for A-Body Mopars

The Holley Street Avenger carburetor is a bolt-on performance upgrade that offers excellent drivability, quick throttle response, and easy tuning for classic Mopar A-body platforms like the Dart, Duster, Demon, and Valiant. Designed with vacuum secondaries, an electric choke, and a no-dribble fuel bowl design, this carburetor is ideal for street-driven small-blocks such as the 318, 340, and 360, as well as mild big-blocks. This comprehensive guide walks through every step of the installation, from tool selection to final tuning, ensuring you extract maximum performance from your engine while avoiding common pitfalls.

Tools and Materials

Having the right tools and parts on hand before starting saves time and prevents frustration. Below is a complete list, including optional items that will make the job smoother.

Required Tools

  • Socket set (1/4-inch and 3/8-inch drive, standard and deep sockets) with extensions
  • Combination wrench set (metric and SAE; carburetor mounting nuts are typically 3/8-inch or 7/16-inch)
  • Fuel line wrench (crows-foot or line wrench recommended) for fragile soft steel or braided lines
  • Torque wrench (1/2-inch drive, able to read 10–25 ft-lbs)
  • Flathead and Phillips screwdrivers
  • Safety glasses and nitrile gloves
  • Shop towels or rags
  • Catch pan for coolant and fuel
  • Billet or phenolic carburetor spacer (performs with thermal isolation for A-body intake manifolds)
  • Fuel pressure regulator (set to 6.5–7.0 PSI for Holley Street Avenger)
  • Vacuum gauge (for tuning idle mixture)
  • Carburetor cleaner and intake surface cleaner
  • Thread-locking compound (blue Loctite) for linkage studs
  • New fuel line hose (3/8-inch) and clamps if original rubber is brittle
  • Distributor vacuum advance hose (if connecting ported vacuum)

Preparation Steps

Proper preparation prevents installation headaches. Begin by ensuring the engine is cool and the battery is disconnected (negative terminal). Remove the air cleaner assembly and any ducting that blocks access to the carburetor. For A-body Mopars, the air cleaner stud often unscrews from the carburetor flange – remove it completely.

Inspect the intake manifold surface for cracks, warpage, or old gasket residue. Use a straightedge to check flatness (especially on aftermarket manifolds). Any debris or high spots will cause vacuum leaks. Clean the surface with carburetor cleaner and a plastic scraper—never a metal one that could gouge the aluminum.

If your engine uses a spread-bore or square-bore intake, confirm the Holley Street Avenger’s throttle bore size matches your manifold’s opening. Most A-body intakes are square-bore (Edelbrock Performer, Mopar M1, factory spread-bores need an adapter plate). Measure the baseplate – Street Avengers are 600 CFM or 770 CFM with 5.125-inch mounting pattern. If needed, purchase an adapter (e.g., Mr. Gasket 1934) and longer studs.

Removing the Old Carburetor

Before unbolting anything, label every vacuum line and linkage rod with tape and a marker. Take a cell phone photo of the current setup for reference. Then follow these steps in order:

  1. Disconnect fuel supply: Use a fuel line wrench to loosen the inlet fitting at the carburetor. Have a rag ready to absorb drips. Cap the line to prevent dirt entry.
  2. Remove throttle linkage: On A-body Mopars, the accelerator cable often attaches to a bellcrank. Unhook the retaining clip and slide the cable end out of the pivot. If you have a kickdown linkage for automatic transmissions, remove that as well – note its position.
  3. Disconnect vacuum hoses: Remove each hose carefully. The distributor vacuum line likely goes to the carb’s ported vacuum nipple (on the front passenger side of the Street Avenger). Label it.
  4. Remove electrical connections: Unplug the electric choke wire (if present) and any electric cut-off solenoid wires.
  5. Unbolt the old carburetor: Using a socket and extension, remove the four mounting nuts (or two nuts on some spread-bore adapters). Lift the carburetor straight up to avoid gasket fragments falling into the intake. Discard the old gasket.
  6. Clean the intake surface: Scrape off any remaining gasket material. Use a shop vac to remove loose debris from the intake runners. Do not allow paper or silicone to enter the engine.

Installing the Holley Street Avenger Carburetor

With the surface clean and dry, you’re ready to mount the new carburetor. The Street Avenger comes pre-calibrated from the factory for a typical small-block, but you may need to make minor adjustments for your specific A-body build.

Step 1: Install Mounting Gasket and Spacer

Place the new gasket (included with the carburetor or a separate open-center gasket) onto the intake manifold. The gasket should align perfectly with the throttle bores. If using a spacer, install it with its own gaskets following the manufacturer’s torque pattern.

Step 2: Mount the Carburetor

Lift the Holley Street Avenger carefully by the baseplate (not the float bowls). Position it over the manifold studs, ensuring the linkage is on the correct side (driver’s side for most A-bodies). Gently lower it onto the gasket. Thread the four mounting nuts by hand – do not tighten yet.

Apply blue Loctite to the studs if needed. Torque the nuts in a crisscross pattern in increments: first to 10 ft-lbs, then final to 18–20 ft-lbs (do not exceed 25 ft-lbs to avoid warping the baseplate).

Step 3: Connect Throttle and Kickdown Linkage

Throttle cable: Hook the cable end into the bellcrank on the driver’s side. Install the retaining clip. Ensure the cable moves freely without binding. Adjust the cable housing so full throttle corresponds to the carburetor’s wide-open stop.

Automatic transmission kickdown: If your A-body has a 727 or 904 transmission, the kickdown linkage must be connected to the carburetor’s throttle arm. The Street Avenger includes a bracket for this purpose. Adjust the rod so that at wide-open throttle, the kickdown lever is fully engaged. Incorrect adjustment can cause transmission damage. Consult a factory service manual for the exact length.

Step 4: Fuel Line Connection

The Street Avenger uses a single 3/8-inch male inlet on the passenger side. Most A-body fuel lines come from the pump on the driver’s side – you may need a pre-bent line or a braided hose kit. If using rubber hose, use high-pressure fuel injection hose and clamps. Tighten the inlet fitting with a fuel line wrench – do not overtighten the brass fitting into the carburetor body (max 20 ft-lbs).

Install an inline fuel pressure gauge and regulator if desired. Holley recommends 6.5–7.0 PSI for the Street Avenger; pressures above 8 PSI can cause flooding.

Step 5: Vacuum Line Connections

Identify the vacuum ports on the Holley (typically four on the front metering block: one large PCV port, three small capped for manifold vacuum). Connect the PCV valve hose to the largest port on the front driver’s side. Connect the distributor vacuum advance to the ported vacuum nipple on the passenger side of the main body (timed to open only after throttle opens). If a vacuum canister or brake booster is used, connect to a manifold vacuum port on the intake manifold or the carburetor base (some Street Avengers have a dedicated port near the base).

Step 6: Choke and Air Cleaner Installation

The electric choke needs a 12V source that is on when the engine is running – connect the red wire to a fused ignition power source (e.g., wiper motor or ballast resistor output). Ground the choke housing with the black wire. Adjust the choke housing cap to the middle notch initially. Install the air cleaner using the supplied stud. Pre-assemble the filter base and wing nut – cross-threading is common, so start by hand.

Final Steps and Initial Startup

Double-check all connections: fuel lines snug, vacuum hoses secure, throttle linkage free, kickdown correctly adjusted, and choke wire live. Reconnect the battery. Turn the ignition key to “on” (do not crank) and listen for the electric choke to click after a few seconds – this confirms power. Check for fuel leaks around the inlet fitting and the bowl plug (use a paper towel – any fuel must be addressed immediately).

Start the engine. Initially, it may crank several times because the fuel bowls are empty – hold the accelerator pedal to the floor (clear flood mode) to let the carburetor squirt fuel. Once running, let it idle at around 1000–1200 RPM (fast idle from choke) until coolant temperature reaches 180°F. If the engine runs rough or stalls, try adjusting the idle mixture screws (located on the metering block below the float bowl) – start with them 1.5 turns out from lightly seated, then adjust equally until highest vacuum is achieved.

After the engine warms, reduce the fast idle speed using the fast idle screw on the choke linkage (target 800–900 RPM in park). Check automatic transmission engagement – a properly adjusted kickdown will cause a slight stumble when shifting into gear; if the idle drops too much, raise the curb idle speed slightly.

Tuning the Holley Street Avenger

For best A-body performance, fine-tune the following settings after installation:

  • Idle mixture: Use a vacuum gauge (9–12 inHg is typical for street cams). Turn each screw in until RPM drops, then back out 1/4 turn until RPM stabilizes.
  • Accelerator pump: Street Avengers have a cam and position adjustment. For off-idle bog, try the #2 cam position (outer holes) and use the blue cam (stiffer spring) for quick response.
  • Float level: With the engine running, remove the sight plug on the side of each float bowl. Fuel should be at the bottom of the threads. Too low can cause hesitation; too high can cause flooding. Adjust by turning the screw atop the bowl while engine is cold.
  • Secondary operation: The vacuum secondary diaphragm can be changed to a stiffer spring for heavier A-body cars. A light spring from Holley (yellow spring) opens quicker for small-blocks with good vacuum.

Troubleshooting Common Issues

A-body Mopar installation quirks often involve linkage clearance and fuel supply. Here are fixes for frequent problems:

Engine Hard to Start or Floods

Check float level – too high overflows the boosters. Also ensure choke is opening fully within 5 minutes of warm-up. Adjust choke pull-off adjustment if the engine floods when hot.

Hesitation on Acceleration

Typically lean condition – increase accelerator pump shot by using a larger cam or moving to the outermost hole. Verify fuel pressure (should be over 5 PSI at the carburetor).

High Idle, Won’t Return to Curb Idle

Throttle linkage binding is common on A-bodies because the cable angle is tight. Check that the throttle arm fully returns to the stop. Lubricate the pivot points. If using a Torker or raised intake, you may need a Holley throttle linkage adapter kit to change the pull angle.

Fuel Leak at Bowl Plug

The Street Avenger’s bowl plug O-rings can shrink. Replace with Holley #26-12 O-ring kit and tighten to 50 in-lbs.

Transmission Shifts Late or Hard

Kickdown linkage adjustment is critical. With the throttle closed, there should be 0.010–0.060 inch slack before the kickdown rod begins to move. Refer to a 1970 Dart service manual for exact procedure.

Performance Upgrades to Consider

Once the carburetor is installed and tuned, maximize your A-body’s potential with these bolt-ons:

  • High-flow air cleaner: A 14-inch open element filter improves flow over a factory dual-snorkel. Watch for hood clearance; use a drop-base on some models.
  • Fuel pressure regulator: Even with stock fuel pump, a regulator (like Holley 12-804) keeps pressure stable and prevents needle-and-seat blowoff.
  • Electric fuel pump: If you have a high-pressure mechanical pump, an electric pump mounted near the tank can supply consistent volume. Pair with a return line.
  • Vacuum gauge permanently installed to monitor engine health and adjust idle mixture seasonally.

External Resources and Further Reading

For detailed specifications on the Holley Street Avenger, including exploded diagrams and tuning guides, visit the official Holley Street Avenger product page. For A-body-specific insight, the For A Bodies Only Mopar Forum has thousands of threads on carburetor swaps, including clearance issues and kickdown tips. Summit Racing also offers a comprehensive listing for the Street Avenger 770 CFM with user reviews and installation notes.

Conclusion

Installing a Holley Street Avenger carburetor on your A-body Mopar is one of the most effective upgrades for improved throttle response and drivability. By following this detailed guide—from preparation to final tuning—you ensure a leak-free install and a fully optimized carburetion system. Take the time to adjust the linkage and jetting for your specific engine combo, and you’ll enjoy reliable, strong performance for years to come. Whether your Mopar is a daily driver, weekend cruiser, or bracket racer, the Street Avenger delivers the classic holley performance with the convenience of vacuum secondaries and electric choke.