Author Topic: Valve Cover PCV Valves and Breathers  (Read 322 times)

Offline Mike81K10

  • Junior Member
  • ***
  • Posts: 968
Valve Cover PCV Valves and Breathers
« on: June 23, 2024, 11:28:30 AM »
I have never thought much about the PCV valves. I always bought and installed them into the valve cover without paying much attention to the specs. Was reading some material online and I understand that the PCV valve can cause the RMS to leak oil, there can be oil blow out, and other problems without the proper valve cover venting. Saw something about a fixed Orifice, etc.

Can someone educate me on this subject. I want to ensure I don't make a mistake on my engines pcv valve or valve cover venting. I bought a; Billet Specialties Valve Cover Breathers BLK21220 and Billet Specialties Valve Cover Breathers BLK20220. Should I return them and get something else?
"Tell me and I forget. Teach me and I remember. Involve me and I learn." -Benjamin Franklin

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6498
Re: Valve Cover PCV Valves and Breathers
« Reply #1 on: June 23, 2024, 02:38:55 PM »
The PCV system is beneficial to overall engine health and service life.  The PCV valve purges crankcase vapors, which are a mixture of air, oil, moisture, and combustion chamber vapors that escape past the piston rings and imposes a slight vacuum on the crankcase (CC).  It helps control moisture accumulation that leads to acid and sludge formation.  The PCV valve fits between either valve cover (or the lifter valley roof) and a balanced manifold vacuum port via a reinforced-wall 3/8" rubber hose.  The valve body contains a spring-loaded sliding check pintle that regulates the flow of CC vapors into the intake manifold where it mixes with the incoming intake charge for subsequent combustion in the cylinders.  The pintle is designed to float between opposing seats against light spring pressure such that it closes toward its inlet (valve cover side) when manifold vacuum is low (e.g., engine off, WOT, and intake backfire) or closes toward its outlet (intake manifold side) when manifold vacuum is greatest (e.g., engine idle RPM and deceleration).  The spring modulates the pintle position between its seats according to the pressure differential on either side of the valve, hence PCV valves are calibrated according to application.  For the greatest CC ventilation benefit, the PCV valve is inserted into a small baffled chamber in the roof of one valve cover and a vented breather is inserted into a small baffled chamber in the roof of the opposite valve cover.  Alternatively, the PCV valve can be centrally located in the lifter valley roof and then both valve covers are vented.  The baffled chambers in the roofs of the valve covers help to isolate the valve and breather from direct exposure to liquid oil thrown from rapidly moving valve train components.  The best valve cover breathers filter incoming air to minimize oil contamination by abrasive particles.  Filters can be internal or external to the breather, however, external filters are more easily serviced.  Due to currently governing emissions laws, the OEM plumbing configuration must be maintained.

Fixed orifice CC ventilation is unique to select engine applications such as the Jeep 4.0L inline six.  IMO PCV systems are superior since they are dynamic and adjust to variable operating conditions on a real-time basis.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Mike81K10

  • Junior Member
  • ***
  • Posts: 968
Re: Valve Cover PCV Valves and Breathers
« Reply #2 on: June 23, 2024, 06:59:48 PM »
bd, I bought these from summit and would like to know if you think they will be sufficient:
Billet Specialties Valve Cover Breathers BLK21220 and Billet Specialties Valve Cover Breathers BLK20220
"Tell me and I forget. Teach me and I remember. Involve me and I learn." -Benjamin Franklin

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6498
Re: Valve Cover PCV Valves and Breathers
« Reply #3 on: June 23, 2024, 11:11:55 PM »
I haven't used either but both should serve your purpose.  The Q&A for BLK21220 suggests the PCV valve may be replaceable with an OEM part (CV774C or CV789C) if necessary.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)