SU HS4 HIF38 HIF4 H4 2.5" Vortex Ram Pipe Velocity Stack

Vortex 2.5" Velocity Stack for SU Carburettors – 35mm Intake

One 3D-printed 2.5" tall “Vortex” velocity stack for SU carburettors with a 35mm intake.

This 2.5-inch SU carburettor intake trumpet is also known as a ram pipe, air horn or velocity stack; confirm the listed SU carb model and 35 mm intake before fitting.

Designed to improve intake performance, this longer Vortex velocity stack provides a smooth bellmouth-style entry into the carburettor and is designed for compatible SU applications.

The IPNG Vortex Design: Spiral Airflow Vanes & A-Series Research

IPNG Automotive developed the Vortex range with reference to established carburettor induction principles explained by David Vizard in Tuning the A-Series Engine, including the importance of inlet shape, smooth air entry and the wider intake system. This is IPNG's own product design, not a collaboration with or endorsement by the author.

The longer 2.5" HS4/HIF38-family inlet trumpet includes the same characteristic spiral vane geometry as the rest of the Vortex range, with extra length requiring careful clearance checks. The internal spiral, or helical flow-guiding, feature is intended to introduce a controlled rotational component (swirl) to the incoming airflow. It is a design objective, not a guarantee of greater power or efficiency on every engine.

Performance note: The airflow effect depends on the complete engine and induction setup. No specific percentage airflow or engine power gain is claimed for this variant.

Fitment

Designed to fit:

• SU HS4
• SU HIF 38
• SU H4
• SU HIF4

These carburettors are commonly used across a wide range of classic British vehicles, including Minis, Jaguars, Triumphs, MGs and other compatible applications.

Key Features

• 2.5" tall Vortex velocity stack
• 35mm intake size
• Designed for compatible SU carburettors
• Designed to improve intake airflow and performance
• Smooth bellmouth-style intake entry
• Longer 2.5" design for applications where additional stack length is desired
• Manufactured from high-temperature-resistant PETG
• Other sizes and lengths available

Installation

Difficulty: ★☆☆☆☆
Estimated Time: Approximately 10–20 minutes, depending on carburettor setup

The velocity stack is designed to fit directly to the compatible SU carburettor using the existing mounting arrangement.

Before use, ensure the stack is securely fitted and that there is sufficient clearance within the engine bay, particularly with the increased 2.5" length.

What's Included

• 1 × 2.5" Vortex velocity stack – 35mm intake

Carburettor NOT included.

Material & Finish

Manufactured from high-temperature-resistant PETG plastic, providing a durable solution for automotive applications.

Custom Options

Other intake sizes and velocity stack lengths are also available.

Please get in touch if you require a different size or configuration.

For the same 35mm SU fitment, compare the 1.5" Vortex stack (IP-0045) or 2" Vortex stack (IP-0044). If your carburettor is an SU HIF44, use the dedicated HIF44 2" Vortex stack (IP-0010) instead.

Important Information

This is an aftermarket IPNG performance component and is not manufactured by or affiliated with SU, Mini, Jaguar, Triumph or MG.

Please ensure the selected velocity stack provides adequate clearance within your specific engine bay and intake setup before installation.

IPNG Part Number

IPNG SKU: IP-0046

Vortex Fitment & Selection Guide

Not sure which Vortex stack is right for your carburettor? Use our Vortex velocity stack fitment & selection guide to compare carburettor fitment, intake or bore size, stack height and IPNG part number.