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EC 309VS Tillotson HR Velocity Stack
309VS EC Infinite Radius Velocity Stack
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EC 309VS Tillotson HR Velocity Stack

Part Number: 309VS
Online Price: $29.95
309VS Velocity Stack for Tillotson HR – 2.5" Billet Aluminum
Availability: In Stock.

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Description

309VS Velocity Stack for Tillotson HR-Series Carburetors – 2.5" OD, CNC Billet Aluminum


Boost your carburetor’s performance with the updated EC 309VS Velocity Stack, engineered specifically for Tillotson HR-Series carburetors. This velocity stack features a precision-machined internal radius that improves airflow dynamics, increasing air velocity and fuel signal to the carb for better throttle response and power.


The latest 309VS design now features a 2.5" outside diameter, replacing the older 2.625" OD version. This allows for compatibility with standard 2.5" air filters, the same used for Box Stock and HL-Series setups—making filter sourcing and maintenance easier than ever.


Perfect for racing and performance builds, this velocity stack is CNC machined from 6061-T6 billet aluminum and includes all required hardware for a clean, professional installation.


Key Features:

  • Enhanced Airflow Design: Radius shape increases air velocity and improves carb signal
  • Redesigned Diameter: New 2.5" OD allows fitment of more common air filters
  • High-Quality Construction: CNC machined from 6061-T6 billet aluminum
  • Includes Hardware: Comes with 1/4-20 socket cap screws for easy installation
  • Optimized for Racing: Ideal for classes where velocity stacks are permitted (check your rulebook)


Compatibility:

  • Fits: Tillotson HR-181, HR-191, HR-196, and other HR-series models
  • Does Not Fit: BM Mikuni 34mm diaphragm carburetors
  • Dimensions: Approx. 2.50” OD × 1.450" ID
  • Bolt Spacing: 3-bolt, spaced at 1.8125” center-to-center
  • Mounting Hardware: 1/4-20 thread socket cap screws (included)


Why Use a Velocity Stack?

Compared to standard filter adapters, velocity stacks provide a smoother and more efficient air path, helping your carburetor breathe better and improving overall engine performance. Where legal, we always recommend using velocity stacks for optimal results.

FAQ

1. What is the 309VS Velocity Stack used for?

It’s designed to improve airflow and fuel signal on Tillotson HR-Series carburetors, boosting performance in karting and small engine applications.


2. What Tillotson carb models does it fit?

The 309VS fits Tillotson HR-181, HR-191, HR-196, and many other HR-series models. It does not fit Mikuni 34mm diaphragm carbs.


3. What’s different about the updated version?

The updated version features a 2.5" OD (down from 2.625"), making it compatible with standard 2.5" air filters, which are more widely available and also used on Box Stock and HL carb setups.


4. What material is it made from?

It’s CNC machined from 6061-T6 billet aluminum, offering excellent strength, heat resistance, and durability.


5. What hardware is included?

The 309VS comes with 1/4-20 socket cap screws and all the mounting hardware required for installation.


6. Is it legal for racing use?

Yes, in many racing classes. However, you should check your rulebook to ensure velocity stacks are allowed in your specific class.

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