Improved Racing - Adjustable PCV Restrictor Valve

Improved Racing's adjustable PCV restrictor allows fine tuning of airflow through PCV lines in recirculated systems without using a traditional PCV valve. In other words, this restrictor completely replaces your factory PCV valve. It's also perfect for LS engines with aftermarket valley covers that do not have a built-in PCV restrictor like the factory cover. This restrictor can also be used to restrict oil flow to a turbocharger to avoid flooding the turbo.

This valve can be used on its own to replace a traditional PCV valve in naturally aspirated engines. In turbocharged applications, combine it with a check valve such as part number DCV-06 or FCV-06-06 to prevent pressurizing the crankcase under boost.

The kit includes five pre-drilled restrictor plates plus a blank restrictor plate with a pilot hole for drilling your own custom hole size. Each plate is laser-marked with the restrictor hole diameter in millimeters. The 2.6 mm restrictor size is the factory restrictor size found in the valley cover of most 2004+ LS1, LS2 and LS3 engines. If using the factory valley cover, drill out the factory restrictor first. We recommend starting with the 2.6mm restrictor and moving up incrementally in size.

The restrictor housing features female -6 O-ring boss ports on each end. We offer several adapter fittings to adapt it to different AN sizes or hose barb sizes, so it will work in virtually any application. 

Usage Notes

This device is for advanced users. You'll need a vacuum gauge to accurately determine the correct restrictor size to use. The goal is to generate as much crankcase vacuum as possible without maxing out your idle air control valve. You may also need to adjust your tune if the PCV flow rate changes significantly from the factory setup or your previous setup. Please see our instruction manual for more details.

Features and Benefits

• Adjustable PCV restrictor with 5 pre-drilled sizes: 2.6mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, and a blank disc with a 1mm pilot hole for custom-drilled sizes.
• Female -6 O-ring boss ports and be adapted to many different fitting types and sizes (male AN, hose barb, quick connect, etc.).
• All aluminum construction with black anodized housing.
• No moving parts for improved durability over traditional PCV valves.