Velocity Stacks, for IDF Weber & HPMX Carbs, Pair 4 Inch

OVERVIEW

When you''re looking to squeeze every ounce of horsepower and throttle response out of your high-performance air-cooled engine, the intake path is the first place you should look. These EMPI 4-inch velocity stacks are engineered specifically for Weber IDF and EMPI HPMX carburetors to optimize the way air enters your engine''s induction system. By providing a smooth, radiused entry point, these stacks significantly reduce air turbulence and create a more laminar flow into the carburetor venturis. This isn''t just about looks; it''s about physics. The 4-inch height is a sweet spot for many builders, as it helps to straighten the air column and increase air velocity, which can lead to improved mid-range torque and a crisper transition when you crack the throttle open on the track or the street.

Beyond the undeniable performance benefits, these velocity stacks provide that iconic "old school" performance aesthetic that defines a high-end VW engine bay. Whether you are running a dual-carb setup on a street-pounding Cal-Look Beetle or a high-revving sand rail, the polished chrome finish adds a professional, show-quality look that tells everyone you mean business. Sold as a pair, these stacks are a direct bolt-on upgrade that installs in minutes but provides a lasting impact on both the drivability and the visual appeal of your machine. Don''t let turbulent, "dirty" air choke out your Weber or HPMX carbs; give them the clean, fast-moving air they crave with these precision-crafted EMPI stacks.

FITMENT

These velocity stacks are designed for dual-barrel downdraft carburetors and fit a wide range of air-cooled Volkswagen models equipped with the following carburetor types:

• Carburetor Compatibility: Weber IDF Series (40, 44, 48) and EMPI HPMX Series (40, 44, 48).
• Volkswagen Type 1: Beetle and Super Beetle (all years with IDF/HPMX conversions).
• Volkswagen Type 2: Bus, Transporter, and Kombi (1950-1979).
• Volkswagen Type 3: Fastback, Squareback, and Notchback.
• Volkswagen Karmann Ghia: All years with upgraded dual carburetors.
• Off-Road: Sand Rails, Dune Buggies, Manx-style bodies, and Baja Bugs.
• Porsche: Porsche 356 and 912 models utilizing Weber IDF carburetors.

SPECS

• Product Brand: EMPI
• Part Number: 43-6054-0
• Total Height: 4 Inches (101.6mm)
• Material: High-quality steel with a durable chrome-plated finish.
• Mounting Style: Bolt-on (utilizes standard carburetor top mounting points).
• Quantity: Sold as a Pair (2 Stacks included).
• Application: Designed for IDF Weber and EMPI HPMX carburetors.
• Function: Increases air velocity and reduces intake turbulence.

PRO TIPS

1. Verify Decklid and Body Clearance

Before finalizing your installation, especially on a standard Volkswagen Beetle or Karmann Ghia, always check your decklid clearance. A 4-inch stack is significantly taller than the standard 2-inch versions often included in carb kits. If you are running a standard decklid without stand-offs, the top of the velocity stack may interfere with the bodywork or the decklid springs. If clearance is tight, you might consider using decklid stand-offs to provide the necessary room and additional cooling air, or ensure your engine mounts are in good condition so the engine doesn''t tilt and hit the body under torque.

2. Protection Against Debris

While open velocity stacks look incredible and offer the least restriction, they provide zero filtration for your engine. If you plan on driving your VW on the street or in dusty off-road environments, we highly recommend installing "wolf whistle" screens or foam "sock" filters over the stacks. Sucking in even a small amount of grit or a stray pebble can cause catastrophic damage to your cylinder walls and piston rings. For show cars, you can run them open, but for a daily driver or a weekend warrior, always prioritize engine longevity with some form of debris protection.

3. Re-Sync and Tune After Installation

Any change to the intake tract can slightly alter the way your carburetors pull air, which can affect your synchronization and mixture. After installing these 4-inch stacks, it is a best practice to use a Uni-Syn or a similar flow meter to ensure both carburetors are pulling the exact same amount of air at idle and off-idle. You might find that the increased velocity requires a slight adjustment to your idle mixture screws to keep the engine running smoothly. Properly synced carbs paired with these stacks will provide a much smoother power band and eliminate that annoying "flat spot" often found in poorly tuned dual-carb setups.