36mm Venturi, for 40 Dcoe Weber Carburetors

Maximize Your Induction Efficiency with the EMPI 36mm Main Venturi

When it comes to fine-tuning your air-cooled VW''s performance, the venturioften referred to as the main chokeis the most critical component inside your Weber 40 DCOE carburetor. These EMPI 36mm venturis are precision-engineered to bridge the gap between streetable drivability and high-RPM power. By narrowing the throat of the carburetor, the venturi creates a localized low-pressure zone based on Bernoulli''s principle, which effectively "pulls" fuel through the main circuit. Choosing the 36mm size is a strategic move for builders looking to maximize top-end airflow on larger displacement Type 1, Type 2, or Type 4 engines without the immediate need to step up to a 45 DCOE body. It allows your engine to breathe deeply during spirited driving and wide-open throttle, ensuring that your dual-carb setup isn''t the bottleneck in your performance equation.

Precision-crafted by EMPI to exacting tolerances, these replacement main venturis are essential for any enthusiast dialing in their fuel map for specific track conditions, altitude changes, or internal engine modifications. If you have recently increased your displacement or installed a higher-lift camshaft, your original, smaller chokes might be restricting your horsepower potential. On the other hand, if you are building a high-revving 1776cc or a torquey 1914cc, the 36mm venturi provides the ideal balance of air volume and signal strength. At Appletree Automotive, we know that every CFM counts. These high-quality alloy venturis provide the smooth, consistent internal surface required to minimize intake turbulence, which leads to superior fuel atomization and a much more responsive power band across the entire RPM range.

Vehicle Fitment and Compatibility

This 36mm main venturi is designed specifically for the Weber 40 DCOE side-draft carburetor and its high-quality clones. It is a staple for performance-oriented air-cooled Volkswagens and various vintage European applications. Fitment includes:

• Volkswagen Beetle: 1950-1979 (With Dual 40 DCOE Side-draft Conversion)
• Volkswagen Karmann Ghia: 1956-1974 (With Dual 40 DCOE Side-draft Conversion)
• Volkswagen Bus / Transporter: 1950-1971 (Type 2 Applications)
• Volkswagen Type 3 (Squareback, Fastback, Notchback): 1961-1973
• Volkswagen Thing: 1973-1974
• Custom Sand Rails and Dune Buggies: Utilizing Type 1 or Type 4 engines with side-draft manifolds.
• Weber 40 DCOE Series: Compatible with Italian, Spanish, and EMPI HPMX/DCOE versions.

Technical Specifications and Materials

Built for durability and flow consistency, these venturis meet the high standards required for competitive racing and reliable street use.

• Venturi Size: 36mm (Internal Diameter at the narrowest point).
• Carburetor Application: 40mm DCOE Side-draft only.
• Material: High-grade die-cast zinc alloy for thermal stability and corrosion resistance.
• Finish: Precision machined smooth-bore finish to reduce air drag.
• Manufacturer: EMPI.
• Part Number: 43-5605-0.
• Quantity: Sold individually (Note: Most dual-carb VW setups require four totaltwo per carburetor).
• Installation Type: Internal slide-fit with set-screw retention.

Pro Tips from the Appletree Garage

Tip 1: The Golden Rule of Venturi Sizing

In the world of Weber tuning, a common rule of thumb is that your venturi size should generally be about 3mm to 4mm smaller than the throttle plate size for a balanced street/strip engine. Running a 36mm venturi in a 40 DCOE is on the "aggressive" side of that rule. This setup is perfect for high-RPM power, but it requires a healthy engine displacement to maintain enough air velocity at low speeds. If you find your engine "stumbling" at low RPMs but screaming at the top end, you have found the sweet spot for a 36mm choke, but you may need to adjust your pump jets to compensate for the slightly weaker low-speed signal.

Tip 2: Always Re-Jet After a Venturi Swap

Never assume your current jetting will work once you swap your venturis. Changing the venturi size fundamentally alters the vacuum signal that pulls fuel from the main jet circuit. When you move to a larger 36mm venturi, the air velocity through the carb decreases at lower RPMs, which usually necessitates a larger main jet to keep the mixture from leaning out. We highly recommend using a Wideband O2 sensor during your first test drive after installation to ensure your Air/Fuel Ratio (AFR) remains safe, especially under heavy load.

Tip 3: Check for Proper Seating and Alignment

When installing these EMPI venturis, cleanliness is paramount. Even a tiny spec of carbon buildup or grit inside the carburetor barrel can prevent the venturi from seating fully. If the venturi isn''t perfectly flush, the set screw (located on the side of the carb body) won''t align properly with the indentation on the venturi. Never force the set screw; if it doesn''t turn in easily, the venturi is likely misaligned. A loose venturi will vibrate, causing air leaks and erratic tuning that can be nearly impossible to diagnose otherwise. Always use a drop of light thread-locking compound on the external jam nut to ensure everything stays tight under the vibration of a high-performance VW engine.