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Velocity stacks – 20V 4age Blacktop throttles


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Velocity stacks to suit 20V 4age Blacktop throttles – Set of 4

Individually machined from a solid round bar these velocity stacks have been carefully designed and tested resulting in a product that not only works excellent but also has the looks to match. Unlike other cheap alternative offerings there arn’t any low quality compromises to save costs such as mismatched “20V universal” types, thin flanges, using slots for the mounting or using something such as an unreliable join to a separate flange.

Lengths available

Normally we offer these different velocity stack lengths:

– 50mm

– (70mm) X: Discontinued

– 100mm

However some of these may not be visible from the drop down menu if they are out of stock at the time. If so then feel free to contact us to check on when these are due to be made available once again.

Design features and advantages

– Machined out of a single solid billet aluminium bar

– Full radius bell-mouth

– Long internal taper down before merging straight just before the flange

– Internal diameter ideal size for throttle opening: no nasty steps.

– Positively located: no adjustment available or needed: no crude slots!

– Different Blacktop and Silvertop versions, the shape and taper was optimised for each

– Parabolic / Exponential curve inlet transition

– Designed and machined in Australia

– Optional fit and an upgrade for inside the OEM Blacktop airbox

– No nonsense semi-polished finish


When the new billet velocity stacks where being designed, they where made from the beginning to be the best there is. These shown here are the result of research, prototype works, testing and then finally CNC machining of the final product. The result of this development was used to update the 100mm rolled type.

The shape of the bellmouth, inlet transition and taper where all optimised to allow for the highest net airspeed possible. During development multiple prototypes where made and put on the flow bench, even the rough test version was able to outflow HRC, IMEC and by a massive 55% the original rubber OEM stacks .

Upgrade for inside original airbox

The 50mm long velocity stacks have a selectable “OEM airbox” modification. This lets them directly replace and upgrade the original rubber type without any custom work. Also without any customisation to the factory fitted airbox. The customer feedback of doing this upgrade has been overwhelmingly positive- real power gains that can be felt without any downsides other than an increase in the induction noise. For anyone still using an airbox this is simply the single best “bang for buck” modification for a 20V Blacktop and a pure bolt on upgrade at that.

Parts compatibility

These velocity stacks have not been compromised in their design to make them a universal design for the different throttle types. So therefore these will only fit up and match internally with those from 20V Blacktop throttle bodies.

A way to double check the type of throttles that are fitted to the engine can be done by measuring between the M8 mounting holes on the top throttle body face where the velocity stacks are normally mounted. There are as follows:

– Silvertop 20V (Gen1+2): 73mm center to center

– Blacktop 20V: 83mm center to center

Installation notes

– Washers should be fitted between the bolt heads and the mounting flanges

– The correct size of the mounting bolts is M8 x 25mm – though a 20mm length is sufficient if the stacks are directly bolted to the throttles without an intake plate / airbox inbetween.

Additional information

Dimensions18 × 18 × 12 cm

50mm, 50mm – OEM Airbox Mod, 70mm, 100mm

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