Weber IDF Main Jet 155

EMPI Weber IDF Main Jet 155 - Precision Tuning for Aircooled VWs

Optimize Your Engine Performance

Achieving the perfect air-fuel ratio is essential for the longevity and power of your aircooled Volkswagen engine. This EMPI Weber IDF Main Jet, size 155, is designed for fine-tuning the high-speed circuit of your carburetors. Whether you are running a daily driver Beetle or a high-compression Dune Buggy, precise jetting ensures smooth acceleration and prevents dangerous lean-out conditions at high RPMs.

Fitment and Compatibility

This main jet is a direct fit for all Weber IDF series carburetors and EMPI EPC carburetors. It is commonly used on VW Type 1, Type 2, and Type 4 engines equipped with dual carb setups. Sold individually, these jets allow you to customize your fuel delivery based on your specific engine displacement, cam profile, and altitude.

Pro Tech Tips from Appletree Auto

1. Identify the Main Circuit: The main jet (155) controls fuel delivery from roughly 2,500 RPM through wide-open throttle. If your VW feels sluggish or "flat" when you step on the gas at cruising speeds, you may need to adjust your main jet size to compensate for the engine's fuel demand.

2. The Air Corrector Relationship: Always remember that the main jet works in tandem with the air corrector jet. While the main jet adds fuel, the air corrector acts as a "bleed" to lean the mixture at very high engine speeds. If you install a 155 main jet and find the top end is too rich, consider increasing your air corrector size to balance the curve.

3. Validate with Plug Readings: After installing new jets, perform a "plug chop" by running the engine under load at the RPM range affected by the main jet, then shutting it off immediately. A healthy "toasted marshmallow" tan color on the spark plug porcelain indicates that your 155 main jets are providing the correct mixture for your aircooled setup.