Frequently Asked Questions

Q:  I’m not familiar with how a PCV valve works.  What does it do?
A:  Ray Bohacz wrote an article for Hemmings Muscle Machines that provides an excellent overview of PCV system functionality.  We recommend reading Ray’s article here for an introduction to PCV systems.

Q:  Why would I want to run dirty crankcase vapors back through my engine?  My bench racing buddies tell me that a PCV valve is really not necessary, and will just dirty up my engine.
A:  There are many false rumors circulating regarding how a PCV valve should function, and whether or not you need to run one.  The facts are that PCV valves have been used on nearly every production automobile for 50+ years, and the need to have a properly functioning PCV system on every vehicle cannot be overstated.  Although at first it may seem counterintuitive, having a properly functioning PCV system will actually keep your engine’s crankcase much cleaner over the long term.  This is firmly established knowledge among automobile manufacturers with many years of data as validation.

Q:  What are some symptoms of an improperly functioning PCV valve?
A:  Typical symptoms include:
Symptom 1: Difficulty tuning at idle.  This often occurs on vehicles with radical camshafts using a mismatched PCV valve, the PCV may be transitioning into cruise mode while the engine is still at idle, causing too much airflow.

Symptom 2: Oil and crankcase vapors constantly accumulating around the valve cover breather. The breather opposite the PCV valve should act as a fresh air inlet if the PCV system is working properly.  Constant oil accumulation around this breather indicates the PCV system is not flowing enough air to evacuate the crankcase, causing excess vapors to force their way out.

Symptom 3:  Accumulation of crankcase sludge and dirty oil.  The long term effect of a PCV system flowing an inadequate amount of air is dirty oil and accumulation of crankcase sludge.  The Dual Flow PCV Valve is the only PCV valve available that lets you tailor the PCV system’s flow rate to your specific engine combination.

Symptom 4:  Oil leaks.  Some, but not all oil leaks may be caused or made worse by excessive pressure in the crankcase.  An improperly matched PCV valve can contribute to crankcase pressure.  The Dual Flow PCV Valve is scientifically proven to keep the crankcase under a slight vacuum more than any stock PCV valve.  See our flow test shootout results for more details.

Q:  PCV valves have been around since the 1960s.  How is the Dual Flow PCV Valve different?
A:  The design of the PCV valve has remained relatively unchanged since its inception over 50 years ago.  A stock style PCV valve has one airflow circuit, which varies airflow from a reduced amount at idle to an increased amount of flow under cruising conditions.  These flow rates, as well as the vacuum level at which the valve transitions from idle to cruise mode, are not adjustable by the end user.  Furthermore, it is difficult to obtain proper flow data to determine which stock style valve (if any) is correct for a modified application.

The M/E Wagner Dual Flow PCV Valve is unique in that it is fully tunable by the end user.  Our patented Dual Flow technology (US Pat. No. 9,376,945) splits airflow into independent idle and cruise circuits, giving you the ultimate in control over your tuneup.  Each circuit is independently tunable to allow for full customization to your specific application.  Flow rate as well as transition vacuum level can be adjusted with the turn of a screw.

Q:  Will a Dual Flow PCV Valve fit my application?
A:  Most PCV Valves for domestic V6 and V8 applications have very similar dimensions.  See Dimensions and Technical Data to check your particular application.  We also offer an Inline Adaptor for engines that do not mount the PCV valve in the valve cover.

Q:  I have been using a stock style PCV valve on my performance engine and it runs fine.  Why do I need a Dual Flow PCV Valve?
A:  Your stock style PCV valve may not be working as well as you think.  Two common issues with an improperly matched PCV valve are idle tuning difficulties and inadequate flow during cruising conditions.  You may have already “worked around” idle tuning difficulties by other means and achieved a usable idle.  Even if this is true, your stock style PCV Valve may not be flowing an adequate amount of air to properly ventilate your crankcase during cruising conditions.

We have found that many stock style PCV valves used on performance applications have a very weak spring, which guarantees the PCV valve will not flow too much air at idle on engines with decreased idle vacuum signals.  While a weak spring stock style PCV valve allows for easier idle tuning, these valves seldom (if ever) transition to higher flow rates during cruising conditions.  Improper crankcase ventilation can lead to several long term problems, such as contaminated oil and accumulation of crankcase sludge.

The Dual Flow PCV Valve is the only PCV valve on the market that can be specifically matched to your engine.  Unlike a stock PCV valve, you can verify it is working properly after tuning is complete.

Q:  My engine has a very weak idle vacuum signal.  Will a Dual Flow PCV Valve work?
A:  Yes.  For engines with a very weak or unstable vacuum signal at idle, the Dual Flow PCV Valve can operate in fixed orifice mode. See Fixed Orifice Mode Tuning for more details.

Q:  I can set the idle flow rate for my specific engine using the idle adjustment screw, how is the flow rate under cruising conditions set?
A:  The cruise flow rate is set by internal porting in the valve.  The Dual Flow PCV Valve will take the idle flow rate set by you, and add the correct amount of additional flow when cruise mode is activated.  This port size is precision machined and was developed based on scientific testing and flow data from a wide variety of applications.

Q:  Does the Dual Flow PCV Valve offer backfire protection for my engine?
A:  Yes.  The Dual Flow PCV Valve uses two stainless steel check balls to positively seal against reverse flow under an intake backfire.

Q:  My engine is worn and has a lot of blowby.  Will my Dual Flow PCV Valve get clogged with contaminants over time?
A:  The Dual Flow PCV Valve is fully rebuildable and cleanable.  It can be completely disassembled for cleaning if necessary.  Rebuild kits are also available.

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