38mm Venturi, for 45 Dcoe Weber Carburetors

OVERVIEW

Precision tuning is the hallmark of a high-performance air-cooled engine, and nothing dictates your power band quite like the venturi size in your Weber carburetors. These EMPI 38mm main venturis, specifically designed for the iconic 45 DCOE Weber series, are the essential component for drivers looking to optimize their induction system for maximum top-end performance without sacrificing essential vacuum signals. By narrowing the throat of the carburetor to a precise 38mm, you are effectively controlling the velocity of the air as it passes through the barrel, creating the necessary pressure drop to pull fuel from the main circuit. This specific size is often the "sweet spot" for large-displacement Type 1 and Type 4 engines that require high CFM flow to support high-RPM horsepower, making it a favorite for drag racers and spirited street enthusiasts alike who demand the best from their dual-carb setups.

When you choose EMPI components from Appletree Automotive, you are investing in decades of air-cooled heritage and engineering excellence. These venturis are manufactured to exacting tolerances to ensure a perfect slide-fit into your 45 DCOE carburetor bodies, preventing the common turbulence issues associated with inferior, off-brand castings. Swapping your venturis is one of the most cost-effective ways to "re-size" your carburetors for a new engine build or a change in driving style. Whether you are moving up from a 36mm to gain more peak power or dialing in a 2275cc monster, these 38mm chokes provide the consistency and reliability required for a stable idle-to-main transition. Don''t settle for a "one size fits all" approach to your fuel delivery; take control of your engine''s volumetric efficiency with the precision and quality that only genuine EMPI performance parts can deliver.

FITMENT

This 38mm main venturi is designed specifically for Weber 45 DCOE carburetors and their high-quality clones. It is a vital upgrade for the following air-cooled VW applications and performance engines:

• Volkswagen Beetle (Type 1): All years equipped with dual 45 DCOE side-draft carburetors.
• Volkswagen Karmann Ghia: Performance builds utilizing side-draft induction systems.
• Volkswagen Bus / Transporter (Type 2): High-displacement upright or pancake engine conversions.
• Volkswagen Type 3 (Squareback, Fastback, Notchback): Custom side-draft configurations.
• Volkswagen Thing (Type 181): Off-road performance builds.
• Custom Engines: Ideal for 1914cc, 2110cc, 2275cc, and 2332cc air-cooled powerplants.
• Porsche 356 & 912: Performance upgrades using 45 DCOE side-drafts.

SPECS

Each EMPI venturi is built to meet rigorous performance standards to ensure your engine runs at peak efficiency. Below are the technical specifications for part number 43-5616-0:

• Carburetor Compatibility: Weber 45 DCOE / EMPI 45 DCOE.
• Internal Diameter (ID): 38mm precision-tapered bore.
• Material: High-grade die-cast zinc/aluminum alloy for thermal stability.
• Finish: Smooth-bore machined finish to minimize intake turbulence.
• Type: Main Venturi (also known as a "Choke").
• Weight: Approximately 0.1 lbs.
• Quantity: Sold individually (two required per carburetor).
• Manufacturer: EMPI (Part # 43-5616-0).

PRO TIPS

1. The Golden Rule of Venturi Sizing: When selecting your venturi size, a common rule of thumb for performance air-cooled engines is to choose a venturi that is approximately 2mm to 4mm smaller than your intake valve diameter. If you are running 40mm or 42mm intake valves on a large-displacement engine, this 38mm venturi will provide an excellent balance of high-RPM airflow while maintaining enough air speed at lower RPMs to keep the fuel atomized. Remember that going too large with a venturi on a small engine will result in a "lazy" throttle response and a flat spot during acceleration, so always match the venturi to your engine''s actual air requirements rather than just "going big."

2. Check for Air Leaks and Seating: When installing new venturis, it is critical to ensure they are seated perfectly flush within the carburetor barrel. Even a tiny gap can cause a vacuum leak or turbulence that disrupts the fuel signal from the auxiliary venturi. Before tightening the locking screw, make sure the main venturi is fully bottomed out. We also recommend checking the condition of your auxiliary venturis (the "boosters") at the same time, as they work in tandem with the main venturi to deliver fuel. If there is any play or wiggle room, you may need to inspect the carburetor body for wear or debris that is preventing a solid mechanical seal.

3. Re-Jetting is Mandatory: Changing your venturi size fundamentally alters the physics of your carburetor. If you are stepping up to a 38mm venturi from a smaller size, you are increasing the volume of air entering the engine, which will lean out your air-fuel mixture. You MUST re-evaluate your main jet and air corrector jet sizes after installation. Generally, a larger venturi requires a larger main jet to maintain the correct stoichiometric ratio. We highly recommend using a Wideband O2 sensor for tuning after a venturi swap to ensure you aren''t running lean at Wide Open Throttle (WOT), which can lead to overheating and engine damage in air-cooled Volkswagens.