A 600 CFM Edelbrock is the typical starting point for a Chevy 305. You can also use 500–550 CFM for stock or mild builds, and 650–700 CFM for higher-rev, performance-oriented setups.
The Chevy 305 is a small-block V8 that powered a wide range of GM cars and trucks. Carburetor sizing matters because it influences idle stability, throttle response, and top-end power. This article outlines practical ranges, model considerations, and tuning tips to help you pick an Edelbrock carb that fits a Chevy 305, whether you’re restoring a classic or boosting a daily driver.
Recommended CFM ranges by build type
Use these ranges as starting points, recognizing that exact values depend on cam choice, intake, exhaust, and how you plan to drive the engine.
- Stock or near-stock 305 (no big cam, mostly daily driving): 500–550 CFM
- Moderate performance cam or mild intake upgrade: 600 CFM
- Aggressive cam, higher RPM range, or performance exhaust: 650–700 CFM
- Very large cams or high-rpm race-oriented builds: 700–750 CFM (rare for a 305, requires careful tuning)
In most street-driven 305 builds, starting at 600 CFM gives a balance of idle quality, throttle response, and top-end power. If you're staying with a stock cam, a 500–550 CFM unit can improve driveability without sacrificing too much top-end. For a cammed, performance-oriented build, a 650–700 CFM carb is a common choice. If you’re chasing peak RPM in a purpose-built form, you may push toward 700–750 CFM, but you’ll need precise tuning and a capable intake/exhaust setup.
Model choice, tuning, and installation considerations
Beyond CFM, the choice of Edelbrock model and how you set up the carb matters. Consider these factors when selecting and tuning your Edelbrock carb for a Chevy 305.
- Carb type: AVS/AVS2 for quick throttle response and broad street power, or Performer-series for simple, broad-range performance. Both are commonly used on 305s with good results.
- Intake compatibility: Pair the carb with a matching Edelbrock intake (e.g., Performer or Performer RPM) that suits your RPM range.
- Throttle response and driveability: If you need strong low-end torque and good idle, a 600 CFM AVS2 is a popular choice; for a very stock look with easy tuning, a 500–550 CFM Performer is sensible.
- Tuning steps: Jetting, squirter size, and accelerator pump calibration govern mixture and response. Start with factory jets and adjust as needed after a test drive. Don’t neglect idle screws and vacuum leaks.
- Fuel system: Ensure adequate fuel delivery; Edelbrock carbs typically run best at about 6–7 psi fuel pressure. Use a reliable pump and regulator if needed.
These considerations help ensure the carb size you choose delivers smooth idle, clean transitions, and strong mid-range torque without sacrificing idle quality. If possible, consult an experienced tuner or dyno facility to tailor the setup to your specific vehicle, cam choice, and performance goals.
Summary
For a Chevy 305, start with a 600 CFM Edelbrock for most street builds, consider 500–550 CFM for stock/mild setups, and 650–700 CFM for more aggressive, higher-RPM builds. The final choice depends on cam duration, RPM range, intake, exhaust, and how you plan to drive. Pair the carb with a compatible Edelbrock intake, tune the jets and accelerator pump, and set fuel pressure around 6–7 psi for reliable performance. With proper setup, a 305 can deliver solid throttle response and good mid-range power without sacrificing idle quality.