Twin 40IDF Ultra HPMX Carburettor Kit - Type 1 Twin Port Engines

The EMPI Ultra Twin 40 HPMX Carburettor Kit is a premium performance upgrade for Type 1 twin port aircooled engines, combining proven HPMX carburettor performance with an advanced “Ultra” linkage and air filter system. Designed for engines 1600cc and above, this kit delivers improved throttle response, smoother operation and increased power output compared to standard carburettor setups.

At the heart of the system are the EMPI HPMX carburettors, featuring independent idle and main circuits with fully changeable jets and venturis. This allows precise tuning across the full rev range, while the adjustable accelerator pump improves off-idle response and acceleration. The inclusion of extended idle jet vent tubes helps prevent common clogging issues, ensuring long-term reliability.

The standout feature of the Ultra kit is the upgraded linkage and air cleaner combination. Cast aluminium air filter bases and tops incorporate the cross-bar mounting directly into the assembly, improving rigidity, throttle accuracy and overall appearance. Paired with offset aluminium manifolds, the carburettors sit square across the engine, allowing the linkage to run parallel with the fan housing for smoother, more consistent throttle control.

Ultra Kit Features

• Cast aluminium air filter bases and tops with integrated linkage mounts
• Aluminium hex bar linkage with steel ball ends and sealed heim joints
• Offset aluminium manifolds for improved alignment and clearance
• Thick wall manifolds ideal for port matching and performance builds
• Chrome air filters with high-flow gauze elements
• Coil relocation bracket and brass fuel tee
• Complete fitting hardware and instructions

Jetting Specification (as supplied)

• 52 Idle Jets
• 115 Main Jets
• 200 Air Correctors
• F11 Emulsion Tubes
• 28mm Venturis
• 50 Accelerator Pump Jets
• 0.55 Exhaust Pump Jets

How It Works
Each carburettor feeds two cylinders independently, dramatically improving air and fuel distribution compared to a single carburettor. The Ultra linkage ensures both carburettors open in perfect synchronisation, while the offset manifolds optimise airflow and positioning. This results in stronger torque, faster throttle response and improved overall engine efficiency.

Important Notes

• Designed for Type 1 twin port engines
• Suitable for engines 1600cc and above
• 30HP style fan shroud required for clearance
• Rolling road tuning and carb balancing strongly recommended
• No choke system fitted

Related Parts

• Carburettor synchronisation tool
• Fuel pressure regulator (essential for correct fuel supply)
• Manifold gasket sets
• Performance ignition upgrades
• Throttle cable and linkage components

To Fit

Aircooled VW

• VW Beetle – 1960–1979 – Type 1 twin port engines (1600cc+)
• VW T2 Splitscreen Bus – 1960–1967 – Type 1 twin port engines (1600cc+)
• VW T2 Baywindow – 1968–1979 – Type 1 twin port engines (1600cc+)
• VW Karmann Ghia – 1960–1974 – Type 1 twin port engines (1600cc+)
• VW Type 181 Trekker – 1968–1983 – Type 1 twin port engines (1600cc+)
• VW Beach Buggy / Baja – 1960–1979 – Type 1 twin port engines (1600cc+)