The Mach 2 Atmosphere Upgrade Kit is designed to convert a GFB Mach 2 valve from full recirculation to atmosphere venting.

This kit includes a trumpet outlet, a firmer spring, and a 30mm hose plug.

For correct atmosphere venting, the Mach 2 piston must remain closed at idle and the recirculation hose must be sealed. The 5930 Atmosphere Conversion Kit provides a 30mm hose plug to block the recirc hose, along with a trumpet that replaces the standard hose outlet on the Mach 2. While the trumpet is not required for operation, it increases the venting sound. A firmer spring (part #6115) is also included.

Mach 2 valves are supplied as standard with a softer spring (part #6116), which is suitable for recirculation setups or engines with an idle vacuum of 18 inHg or less. If the piston remains closed at idle with the existing spring installed, no spring change is necessary.

If the piston sits partially open at idle even with maximum spring pre-load applied, the firmer spring included in this kit should be fitted. This helps prevent drivability issues such as stalling or backfiring when converting to atmosphere venting.

Compatibility:
Suits GFB Mach 2 part numbers T9100, T9101, T9102, T9104, T9105, T9135.