Vortex Ram Pipes, Velocity Stacks & Intake Trumpets – SU, Weber & Dellorto Fitment Guide

Looking for a carburettor ram pipe, velocity stack, intake trumpet, air horn or bellmouth? These are common names for the flared inlet fitted to a carburettor to help guide the incoming air. IPNG Automotive's Vortex range includes dedicated versions for SU HS2, HS4, H4, HIF4, HIF38 and HIF44 carburettors, plus selected Weber DCOE and Dellorto applications.

To choose the correct product, identify the carburettor model and verify the mounting dimensions first, then choose a stack length that fits the available engine-bay or airbox space. This guide lists each current IPNG product, its part number, stated fitment and a direct link to the individual product page.

What Makes IPNG Vortex Ram Pipes Different?

Developed Around Established A-Series Induction Principles

The IPNG Automotive Vortex range has been developed with reference to the carburettor induction and ram-pipe principles discussed by renowned engine-tuning author David Vizard in his book Tuning the A-Series Engine. His research and practical guidance highlight why the shape of a carburettor inlet, entry radius, inlet restriction and overall induction arrangement matter when developing an engine for effective airflow.

Our aim is to apply those established principles to a modern, purpose-designed intake trumpet rather than treat a ram pipe as purely cosmetic. The design is by IPNG Automotive; referencing Vizard's research does not imply that he designed, tested or endorsed these products.

The Signature Vortex Spiral – Helical Airflow Guide Vanes

Every IPNG Vortex velocity stack in this range features the distinctive internal spiral (helical) flow-guiding vane design alongside its flared bellmouth entrance. The curved vanes are intended to guide incoming air along a controlled, rotational path as it approaches the carburettor throat, influencing the flow direction and entry behaviour rather than simply presenting an open tube.

This is the defining feature behind the Vortex name: a deliberate airflow-guiding geometry developed as part of the IPNG intake trumpet, ram pipe and air horn range. Its purpose is to help manage the incoming air, but the effect on airflow, mixture behaviour, torque or power depends on the carburettor, engine, filtration and full inlet setup. A spiral design alone does not guarantee a performance increase.

Design and Testing Are Different Claims

IPNG has reported an approximately 5.2% intake airflow increase from its development testing on selected Vortex configurations. The tested designs named later in this guide are IP-0010, IP-0044 and IP-0045. This is a reported airflow comparison under the manufacturer's development conditions, not a claim of 5.2% more horsepower or a result established for every Vortex product. See the development testing section below for the relevant products.

Ram Pipe, Velocity Stack, Intake Trumpet, Air Horn or Bellmouth: What's the Difference?

These terms are often used interchangeably by Classic Mini owners and carburettor suppliers. In the context of the IPNG Vortex range, they refer to a flared carburettor inlet designed to smooth the transition of air into the carburettor. Intake trumpet, inlet trumpet, carburettor trumpet, ram pipe, air horn and velocity stack are useful search terms for the same broad type of component. A bellmouth specifically describes the radiused entry shape.

A stub stack is generally a shorter form of inlet trumpet; it is not automatically interchangeable with a 1.5", 2" or 2.5" product. American product listings may use the spelling carburetor instead of carburettor. None of these names establishes compatibility by itself.

How to Identify an SU HS2, HS4, HIF38 or HIF44 Carburettor

The carburettor throat diameter and float-chamber arrangement are useful identification clues, but always check the carburettor identification markings and the actual mounting face before ordering a ram pipe.

Important dimension distinction: the 35mm measurement described on IPNG's HS4/HIF38 stack listings relates to the listed stack intake/fitment specification; it is not the nominal 38mm bore designation of the carburettor. Compare the actual mating dimensions with the product before fitting. A similar stack length does not make parts for different carburettor families interchangeable.

Vortex Velocity Stack Quick Fitment Table

Important: stack height alone does not determine fitment. A 2" HIF44 stack is not the same product as a 2" 35mm HS4/HIF38 stack or a 2" Weber/Dellorto stack.

SU HS2 Ram Pipes / Intake Trumpets – 1.5" and 2" Vortex Options

For a SU HS2 carburettor, choose the HS2-specific IPNG Vortex design rather than a visually similar HS4 or HIF44 stack. The HS2 is a 1¼" (approximately 32mm bore) SU carburettor, commonly found on Classic Mini and other British classic installations. Both versions are supplied as one ram pipe; they do not include a carburettor or air filter.

SU HS2 1.5" Vortex Ram Pipe – IP-0053

The shorter 1.5" HS2 stack (IP-0053) is useful when available intake space is more restricted. Check the mounting and surrounding clearance on your particular HS2 installation.

SU HS2 2" Vortex Velocity Stack – IP-0060

The longer 2" HS2 stack (IP-0060) needs more room. Select the length based on your actual filter, airbox and engine-bay arrangement rather than assuming a particular power increase.

SU HS4, HIF38, HIF4 & H4 – 35mm Vortex Range

The 35mm SU range is designed for compatible SU HS4, HIF38, HIF4 and H4 carburettors. Three stack lengths are currently available, allowing the same carburettor family to be matched to different packaging and engine-bay clearance requirements.

• IP-0045 – 1.5" Vortex velocity stack: the shortest current 35mm option and useful where available space is more restricted.
• IP-0044 – 2" Vortex velocity stack: the middle-length option for the same 35mm SU fitment.
• IP-0046 – 2.5" Vortex velocity stack: the longest current 35mm option and therefore requires the most clearance around the carburettor.

Choose between these three lengths only after confirming that your carburettor is one of the compatible 35mm SU types. Check clearance to the bodywork, bonnet, bulkhead, filter arrangement and surrounding components before ordering, particularly with the 2.5" stack.

SU HIF44 – Dedicated 2" Vortex Stack

The SU HIF44 uses its own dedicated Vortex product: IP-0010. The HIF44 is commonly described as a 1¾" SU carburettor and should not be confused with the 35mm HS4/HIF38/HIF4/H4 range above.

If you have an HIF44, select the HIF44-specific stack rather than choosing one of the 35mm products simply because the stack height is also 2".

Weber DCOE40 & Dellorto DHLA40 – 40mm Pair

IP-0020 is supplied as a pair of 2" Vortex velocity stacks with a 40mm bore and 65mm mounting-stud centres. The primary verified applications are Weber DCOE40 and Dellorto DHLA40.

The same 65mm stud-centre pattern is also commonly encountered on some other 40mm carburettor applications, including Dellorto DRLA40, Weber DCOM40 and Weber IDF40. For these additional applications, confirm both the 40mm bore and 65mm stud-centre measurement before purchase rather than relying on the model name alone.

Weber DCOE45 & Dellorto 45mm Applications – 45mm Pair

IP-0021 is the larger 45mm Vortex pair, also 2" tall with 65mm mounting-stud centres. Current listed fitment includes Dellorto DHLA45/48, Dellorto DRLA45/48, Weber DCOE45 and Weber IDF44/48.

Because carburettor families and aftermarket setups vary, always compare your carburettor and mounting dimensions with the product listing before ordering.

How to Choose the Correct Stack Height

Where more than one stack height is offered for the same carburettor family, the first practical consideration is physical clearance. Measure the available space from the carburettor face to any bonnet, bulkhead, bodywork, filter, airbox or other nearby component.

The current 35mm SU family is offered in 1.5", 2" and 2.5" lengths. This guide does not assume that one length will produce a specific torque or power characteristic on every engine, because the result depends on the complete intake, carburettor, manifold and engine combination. Select the length that suits your known setup and available space, and seek appropriate tuning advice where the induction system is being developed as part of a performance build.

Vortex Airflow Development Testing

IPNG Automotive reports an approximately 5.2% improvement in intake airflow compared with a standard A-Series intake setup from development testing of selected Vortex designs. This tested figure applies to the products for which IPNG has confirmed that development testing: IP-0010 HIF44, IP-0044 2" 35mm SU and IP-0045 1.5" 35mm SU.

This is a reported airflow measurement, not a measured horsepower or torque gain. The result can vary with the individual carburettor, engine and intake configuration. The same 5.2% figure is not being claimed for IP-0053, IP-0060, IP-0046, IP-0020 or IP-0021.

Air Filtration

A velocity stack shapes the airflow entering the carburettor; it does not remove the need for appropriate filtration where filtration is required. For exposed engine bays or vehicles regularly used in dusty environments, use a suitable filter arrangement to reduce the risk of airborne dirt and debris entering the engine.

Always make sure any filter used provides suitable clearance around the bellmouth and is compatible with the particular carburettor and stack arrangement.

Before You Order

1. Identify the carburettor model. Do not select a stack from vehicle make/model alone, as many classic cars have been modified over time.
2. Confirm the intake or bore size. The HS2, HS4/HIF38-family, HIF44, 40mm Weber/Dellorto and 45mm Weber/Dellorto products are different fitment families.
3. Check the mounting arrangement. For the Weber/Dellorto products, confirm the listed 65mm stud-centre spacing.
4. Measure available clearance. This is particularly important when choosing between the 1.5", 2" and 2.5" 35mm SU stacks.
5. Check filtration requirements. Plan the complete intake arrangement rather than treating the stack in isolation.

Common Questions About Classic Mini Ram Pipes and Velocity Stacks

Are a carburettor ram pipe, velocity stack and intake trumpet the same thing?

These names are commonly used for a flared carburettor inlet or bellmouth. Exact designs differ, and the correct fit depends on the carburettor model, inlet diameter, mounting features and available space.

Does an SU HS2 velocity stack fit an HS4 or HIF44?

No fitment should be assumed simply because the parts look similar. IPNG offers HS2-specific, HS4/HIF38-family and HIF44-specific options. Identify your carburettor and check the mounting dimensions before ordering.

Which height is best: 1.5", 2" or 2.5"?

Choose the correct carburettor fitment first, then check physical clearance and filter placement. Changing inlet length can affect engine behaviour, but no particular torque or power gain is guaranteed by stack length alone.

Does a Vortex velocity stack replace an air filter?

No. A ram pipe shapes incoming airflow; it does not provide effective filtration. Select a suitable filter or airbox arrangement, particularly for road use or dusty environments.

Are the Weber/Dellorto Vortex ram pipes sold singly or as pairs?

The 40mm IP-0020 and 45mm IP-0021 listings each include a pair of two 2" stacks. IPNG's SU stack listings in this guide are sold as one stack each.

What makes the Vortex inlet design different?

The Vortex design combines a radiused bellmouth with internal flow-guiding features on selected products. Its intention is to control airflow entering the carburettor. IPNG has reported development-test airflow improvements for specified designs, but results vary by engine and intake setup; untested products are not assigned the same percentage.

Shop the Vortex Range

View all current Vortex velocity stacks and carburettor ram pipes, or use the fitment table above to go directly to the appropriate IPNG product.

If your carburettor or required configuration is not shown, contact IPNG Automotive with the carburettor model, bore or intake measurement, mounting dimensions and available stack length so the requirement can be checked accurately.