Vortex Velocity Stack Fitment & Selection Guide

The IPNG Automotive Vortex velocity stack range covers several different SU, Weber and Dellorto carburettor families. The correct stack should be selected by carburettor type and intake or bore size first, then by stack height and available engine-bay clearance.

This guide brings the current Vortex range together in one place so you can identify the correct product without relying on appearance or stack length alone. If you already know your carburettor model, use the table below to go directly to the matching IPNG product.

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 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 Testing

Development testing on specific Vortex designs has shown an approximately 5.2% improvement in intake airflow over the standard A-Series setup. 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.

The result can vary with the individual carburettor, engine and intake configuration. The same 5.2% figure is not being claimed here for IP-0046 or the Weber/Dellorto products.

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 35mm SU, 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.

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.