6 Velocity Stacks, for IDF Weber & HPMX Carbs, Pair, EMPI

OVERVIEW

Unlock the full potential of your high-performance air-cooled engine with these premium EMPI 6-inch velocity stacks, specifically engineered for Weber IDF and EMPI HPMX carburetors. In the world of air-cooled VW performance, airflow is king, and these air horns are designed to do much more than just look impressive under the decklid. By creating a smooth, radiused entry point for incoming air, these stacks significantly reduce turbulence at the mouth of the carburetor. This allows for a more laminar flow into the venturis, which increases air velocity and improves the signal to the fuel circuits. Whether you are running a dual 40, 44, or 48 setup, these 6-inch tall stacks provide the necessary column of air to stabilize intake pulses, resulting in crisper throttle response and a noticeable gain in top-end horsepower where your engine needs it most.

Crafted with a high-quality chrome finish, these velocity stacks provide that iconic "old school" race look while offering the durability required for the harsh environment of a VW engine bay. The 6-inch height is particularly effective for larger displacement engines that demand a high volume of air at higher RPMs. By lengthening the intake tract, these stacks help tune the resonant frequency of the intake system, which can help smooth out flat spots in your acceleration curve. Sold as a pair, these are a direct bolt-on for any IDF or HPMX pattern carburetor, making them an essential upgrade for any Type 1, Type 2, or Type 3 enthusiast looking to squeeze every ounce of performance out of their dual-carburetor configuration. When you demand the best for your street-strip machine or your weekend cruiser, EMPI delivers the precision and style that have made them a staple in the VW community for decades.

FITMENT

These velocity stacks are designed for carburetors with the Weber IDF bolt pattern and are compatible with the following models and applications:

• Weber Carburetors: 40 IDF, 44 IDF, and 48 IDF series.
• EMPI Carburetors: 40 HPMX, 44 HPMX, and 48 HPMX series.
• Volkswagen Type 1: Beetle, Karmann Ghia, and Thing (all years equipped with dual IDF/HPMX setups).
• Volkswagen Type 2: Bus, Transporter, and Kombi (1950-1979 equipped with dual IDF/HPMX setups).
• Volkswagen Type 3: Notchback, Squareback, and Fastback.
• Dune Buggies & Sand Rails: Any custom air-cooled application utilizing IDF or HPMX carburetors.
• Note: Due to the 6-inch height, clearance must be verified for specific engine compartments, especially in standard Beetle engine bays without decklid stand-offs.

SPECS

• Overall Height: 6 Inches (152.4mm).
• Material: Heavy-duty steel construction.
• Finish: High-luster polished chrome.
• Base Type: Standard IDF / HPMX bolt pattern.
• Quantity: Sold as a pair (2 stacks per package).
• Mounting: Bolt-on design for easy installation over carburetor studs.
• Function: Velocity enhancement and turbulence reduction.
• Manufacturer Part Number: 43-6056-0.

PRO TIPS

1. Verify Decklid Clearance Before Closing

A 6-inch velocity stack is significantly taller than the standard 2-inch versions often found on base kits. Before you slam your decklid shut, always perform a "clay test" or carefully measure the distance from the top of the carburetor to the underside of the bodywork. In many standard VW Beetles, these tall stacks will require the use of decklid stand-offs or a "pop-out" style decklid to prevent the stacks from hitting the metal. If the stack is too close to the decklid, it can actually restrict airflow rather than improve it, defeating the entire purpose of the upgrade. Always ensure you have at least 2 to 3 inches of "dead space" above the stack for optimal air intake.

2. Protect Your Internals from Debris

Running open velocity stacks looks incredible and provides the least amount of intake restriction, but it also leaves your engine vulnerable to road grit, pebbles, and debris. Since these 6-inch stacks are often used in performance applications, we highly recommend using "pantyhose" style mesh covers or dedicated velocity stack filter screens if you plan on street driving. Even a small piece of debris entering the venturi at high RPM can cause catastrophic damage to your cylinders and valves. If you are racing on a dirt track or in a sandy environment, consider using a specialized "over-stack" air filter system to maintain the velocity benefits while protecting your investment.

3. Re-Sync and Re-Tune for Maximum Gains

Installing taller velocity stacks changes the resonance and the air-fuel demand of your engine, particularly in the mid-to-high RPM range. Once you have installed these 6-inch stacks, it is vital to re-synchronize your dual carburetors using a high-quality Uni-Syn or snail-style sync tool. Don''t be surprised if you need to slightly adjust your main jets or air correctors to compensate for the improved airflow characteristics. The longer intake column can sometimes lean out the mixture at high speeds, so checking your spark plugs for a "lean" condition after a few high-speed pulls is a smart move to ensure your engine stays healthy and powerful.