32mm Venturi, for 40 Dcoe Weber Carburetors

OVERVIEW

Precision tuning is the difference between a Volkswagen that simply runs and one that screams down the pavement with crisp, immediate throttle response. This EMPI 32mm Main Venturi is a critical component for anyone running 40 DCOE Weber carburetors, serving as the heart of the carburetor''s air-metering system. The venturi is responsible for creating the pressure drop necessary to pull fuel from the main circuit and atomize it into the airstream. By selecting a 32mm size, you are effectively narrowing the throat of your 40mm carburetor to increase air velocity, which significantly improves the "signal" sent to the fuel jets. This results in a much more responsive engine at lower and mid-range RPMs, making it an ideal choice for street-driven air-cooled engines that need to balance daily drivability with high-performance output.

At Appletree Automotive, we know that "one size fits all" never applies to high-performance carburation. Upgrading or replacing your venturis allows you to fine-tune your intake charge to match your specific engine displacement, cam profile, and head flow characteristics. If you find that your engine stumbles off the line or feels "lazy" when you tip into the throttle, your current venturis might be too large, causing a drop in air velocity. Switching to these precision-machined 32mm chokes ensures that the air speed remains high enough to keep the fuel properly suspended in the intake charge, preventing puddling and ensuring a smooth power band. Whether you are rebuilding a vintage set of Italian Webers or fine-tuning a brand-new EMPI setup, these venturis provide the consistency and accuracy required for professional-grade engine calibration.

FITMENT

This 32mm venturi is designed specifically for the following applications:

• Carburetor Models: Authentic Weber 40 DCOE Series, EMPI 40 DCOE Reproductions, and select 40mm Side-Draft clones.
• VW Type 1: Beetle, Karmann Ghia, and Thing (equipped with dual 40 DCOE side-draft kits).
• VW Type 2: Bus, Transporter, and Campmobile (1950-1979 with side-draft manifolds).
• VW Type 3: Squareback, Fastback, and Notchback (common in dual side-draft racing configurations).
• Universal: Any custom air-cooled or water-cooled engine utilizing 40mm DCOE platform carburetors.

SPECS

• Internal Diameter (Choke Size): 32mm.
• External Diameter: Precision machined to fit 40mm DCOE carburetor bodies.
• Material: High-grade die-cast aluminum alloy for thermal stability and corrosion resistance.
• Manufacturing Part Number: 43-5603-0.
• Quantity: Sold individually (Each).
• Function: Main Venturi (also known as the "Main Choke").
• Compatibility: Designed for use with standard Weber-style auxiliary venturis.

PRO TIPS

1. The 2mm to 4mm Rule of Thumb

When selecting a venturi for your 40 DCOE, a common rule of thumb is to choose a size that is 2mm to 4mm smaller than the intake valve diameter, or roughly 80% of the carburetor''s total bore size. A 32mm venturi in a 40mm carb is the "sweet spot" for 1600cc to 1914cc engines that spend most of their time on the street. It provides enough airflow for top-end power while maintaining the high air velocity needed for a clean, crisp transition from the idle circuit to the main circuit. If you go too large (like a 36mm), you might gain 2-3 horsepower at 6,000 RPM but lose significant torque and "drivability" in the 2,000 to 3,500 RPM range where you drive most often.

2. Re-Jetting is Mandatory After Venturi Changes

Never change your venturi size without also adjusting your main jets. Because a 32mm venturi increases the air velocity compared to a larger size, it creates a stronger vacuum signal. This stronger signal will pull more fuel through the same size jet. Typically, when you decrease the venturi size, you may need to slightly decrease the main jet size to maintain the correct air-fuel ratio. Conversely, if you are stepping up to a 32mm from a 28mm, you will likely need to increase your main jet size. Always use a wideband O2 sensor or check your spark plugs immediately after a venturi swap to ensure you aren''t running too lean or too rich.

3. Proper Seating and Alignment

When installing these 32mm venturis, cleanliness is paramount. Even a tiny speck of dirt or a burr inside the carburetor barrel can prevent the venturi from seating perfectly flat. If the venturi is canted or loose, it can cause "pulsing" in the fuel delivery and make the carburetor impossible to sync. We recommend lightly lubricating the outer surface of the venturi with a tiny amount of thin oil to help it slide into place. Ensure the locking screw (or the auxiliary venturi, depending on your specific DCOE model) is properly aligned with the machined indentation on the venturi to lock it firmly in place. A vibrating venturi will eventually wear out the carb body, so a snug, secure fit is essential for long-term performance.