High-Flow Dual Source PCV Check Valve for Turbocharged Engines, -6 ORB

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  • High flow, low cracking pressure flapper style check valve with dual inlet and dual outlet ports.
  • Ideal for PCV systems, allows connecting two vacuum sources to the crankcase which protecting against boost in forced induction applications.
  • -6 ORB connections.
  • Very low 0.04 PSI cracking pressure.
  • Holds 300+ psi of back pressure.
  • 1,000+ psi max operating pressure in direction of flow.
  • Exceeds most military specification requirements.
  • Made in USA.
  • Lifetime Warranty.

Lifetime Warranty

Part # DCV-06
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A Dual Vacuum Source Check Valve for Turbocharged Engines


Improved Racing's patent-pending DCV-06 check valve enables two independent vacuum sources to be connected to your crankcase for evacuating blow-by gases.




  • Maximize crankcase vacuum at all times, while protecting the crankcase from boost pressure.
  • By sealing or restricting the crankcase fresh air inlet, crankcase pressure is lowered significantly, increasing horsepower.
  • Patent-pending, ultra-low flow restriction valve design.
  • Extremely low cracking pressure of just 0.04 PSI.
  • Safely handles over 300 psi of boost pressure.
  • Robust stainless steel and anodized aluminum construction.
  • FKM seals for compatibility with most fluids and operating temperatures up to 302°F (150°C).
  • Near-zero leak rate.


Theory of Operation


This innovative valve is perfect for turbocharged engines, where intake manifold vacuum cannot be used to vent the crankcase under boost. Instead, you can connect your crankcase to both the intake manifold (for a strong vacuum source under low engine load) and the turbocharger intlet (for a venturi vacuum source under boost) at the same time. The dual check valve will ensure the source with the strongest vacuum will actively evacuate crankcase gases, while holding up to 300 psi of boost pressure.


The clean air inlet (or vent line) to the crankcase can be completely sealed off to maximize crankcase vacuum, minimizing crankcase pressure. Reducing crankcase pressure will result in less windage and drag on the rotating assembly, increasing horsepower to the wheels. If allowing some clean air to vent the crankcase is still desired, a non-venturi vent line can be connected to the intake piping with a restrictor valve (see Improved Racing part # FO-06R).


DCV-06 Cutaway View


DCV-06 Cutaway View - Boost Condition

Ultra-Low Flow Restriction

Most check valve designs - including poppet check valves, ball check valves, diaphragm check valves, piston check valves, and others - are restrictive, resulting in a pressure drop across the valve even when fully open.


Improved Racing's check valves use a flapper design, originally developed for military jet engine turbines, that swings completely out of the fluid's flow path, adding virtually no flow restriction. These check valves were further optimized for low restriction at high flow rates using flow simulation software and were designed to exceed most military specification requirements.


Improved Racing's patent-pending design incorporates innovations that allow the swinging door design to be implemented in a compact valve size using small components.

FCV-06 Closed Position

High-Flow Check Valve in Open Position, Unrestricted Flow

* Cutaway diagram of single inline check valve shown.


Low Cracking Pressure

This flapper style valve has a very low cracking pressure of less than 0.04 psi, making it ideal for applications such as PCV systems. Higher cracking pressures are also possible by replacing the torsion spring.

High Holding Pressure

The valves have been tested to 1,000 psi of checked holding pressure without catastrophic failures or excessive leakage. This allows us to conservatively rate these valves to hold 300+ psi of checked pressure under normal operating conditions. For comparison, the military-grade check valves we tested failed catastrophically with complete pressure loss at less than 200 psi.

Constructed from Durable Materials

Every internal component (hinge, spring, hinge pin, and gasket core) is made from stainless steel to ensure long lasting, reliable performance and compatibility with just about any fluid, including corrosive fluids. 


The check valve's gasket seal is made from FKM (Viton®) rubber bonded to a stainless steel core, giving it a high operating temperature of up to 302°F (150°C). It's also highly chemical resistant and compatible with practically all fuel types.

Near-Zero Leak Rate

Unlike typical valves with an all-metal construction, Improved Racing's valves provide a near-zero leak rate thanks to the FKM (Viton®) rubber seal. This means your engine will receive fuel or oil pressure immediately with no priming required.

Features and Specifications

  • Flapper design allows for very high flow with low restriction.
  • -6AN female O-ring boss ports with one plug included.
  • FKM (Viton®) rubber seal.
  • All stainless steel internal components for compatibility with a wide range of fluids.
  • 6061-T6 billet aluminum body with black MIL-A-8625 Type II anodized finish.
  • Laser marked with flow direction and hinge location per military specification.
  • Maximum operating backflow holding pressure of 300+ psi, burst backflow holding pressure of over 1,000 psi.
  • Maximum unchecked (normal direction of flow) operating pressure of over 1,000 PSI.
  • -40°F to 302°F operating temperature range.

Flow Diagram

DCV-06 Flow Diagram


DCV-06 Dimensions


  • Ideal for use with crankcase ventilation systems in turbocharged engines.
  • May also be used with fuel systems, air systems, and coolant systems.

Parts Included

  • 1 x DCV-06 dual source check valve
  • 1 x PO-06 -6AN O-ring boss plug (to plug second feed port when not in use).
Part #
Improved Racing
Primary Material
6061-T6 aluminum
Type II Anodized
Fitting Angle
Connection A Type
Connection A Size
Connection A Gender
Connection B Type
Connection B Size
Connection B Gender
Tee Connection Type
Tee Connection Size
Tee Connection Gender
Maximum Operating Temperature
302°F (150°C)
Minimum Operating Temperature
-40°F (-40°C)
Maximum Operating Pressure
300 psi (20.68 bar)
O-Ring / Gasket Material
FKM (Viton)
on installation only
Breather and vent lines
Fuel (in-tank)
Fuel (outside of tank)
Gauge and sensor lines
High temperature applications
Hydraulics: low pressure (return lines)
Vacuum lines
Coolant & water lines
Other oil water and air systems
Fluid Compatibility
Air and gas
Brake Fluid
Engine oil
Ethanol-based fuels (E85+)
Ethanol/gasoline mixtures
Gear oil
Nitrous Oxide
Power Steering Fluid
Racing fuels
Transmission fluid
Standards & Certifications
Milspec Type II Anodizing
O-Ring Boss Threads per SAE J1926-3 & ASME B1.1
O-Ring Boss Threads per SAE AS5202
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