Basic Breather system
Dual PCV System

Method 3   (Breather System With A Remote Breather and 5/8" line):

    In other experiments, I had tapped the top of a Motorcraft cap (FMS-M-6766-F302).  
    Its the basic chrome one that you can find in most places.  However, the chrome is
    merely a cover to the solid plastic cap and it will come off.  I still use this as my main
    ventilation point vs the hose nipple off the side of the oil fill tube.  The stock Mustang
    oil fill cap is designed to click and stop once it's tight and there is no simple way to tap
    the stock cap for a larger fitting.  At the Method 2 level, the hose nipple at the side of
    the oil fill tube is also 3/8" and it should work properly without the need for the cap.  
    Moving on to Method 3 requires the ability to modify an oil fill cap to except a larger
    fitting or another method of running a larger vent line (IE; drill new hole, -8+ AN
    fitting..).  Additional modifications to the driver side valve cover may also be needed.  
    (Shown to the left is the oil fill cap with a 3/8" NPT heater hose fitting).  

While experimenting with the dual PCV valve set-up I modified my driver side valve cover.  I have a 3/8" hose barb
fitting that exits from the rear of the valve cover with a baffle installed.  I also have a second fill hole that was drilled
in the front of the driver side valve cover.  These modifications are shown in detail on the
Dual PCV Valve page.  

In Method 2, I also tried to incorporate the rear valve cover fitting into the venting scenario.  (Venting through 3 holes
using all 3/8" line and all tied together with the remote breather).  The results were no different than with just the
PCV valve and passenger valve cover venting.  Using Method 2 with my supercharger, I found that with extended
higher RPM runs, the oil mist and vapor still found a way to escape.  This was using my modified cap with a 3/8" hose
barb fitting and the remote breather.  The smaller 3/8" system just couldn't keep up with the pressure build up while
consistently running the engine hard.  I had oil being pushed out between the not so tightly sealed oil fill cap and the
top of the oil fill tube lip.  The oil never escaped at the remote breather and I've never had to drain the remote

Hitting the hardware and auto parts stores once again in search
of a better way, I decided to try 5/8" hose.  Engine builders have
been installing larger lines for venting for a long time and I
figured I'd give it a try.  I've tried to keep costs down as I've
experimented vs. spending money on -10 or -12 fittings and lines
only to find it didn't work to my satisfaction either.  The current
setup still makes it easy to swap back to a stock PCV system if
you need to have your vehicle inspected or pass emissions.   

Most of the parts used to create this system can be found in
the "Help" and PCV sections of your auto parts store.   The
fittings and lines are primary from PCV hose connections,
heater hose fittings, connectors, and lines.

    I'm guessing that 98% of the people out there don't have any modifications to
    their driver side stock EFI valve cover.  I'll explain how to put it together using
    the stock PCV valve and valve cover fill tube locations, and then detail my
    additional follow through.   

The above photo shows the different components I used to put the PCV valve section together with my modified
driver side valve cover.  The upper hose, from left to right, includes a 5/8" 'T' heater hose connection, 5/8" heater
hose, a gutted PCV valve, and 3/8" hose.  The middle two fittings merely show what I used outside of the hose itself
before being installed.  The bottom single upright fitting is a PCV connector and fits into the stock PCV valve grommet
in the lower intake.  A short section of 5/8" hose is used to connect the bottom fitting to the main upper hose.  The
gutted PCV valve and 3/8" hose is used to connect to my modified driver side valve cover.  The larger end of the PCV
valve fits snug into the 5/8' hose.  If you are installing a system without driver side valve cover modifications you
could swap the 'T' fitting for a 90 deg PCV valve elbow or just attach the lower fitting directly to the 5/8" hose.  The
5/8" hose is more cumbersome due to its size and the 90 deg fitting may work better in the tight space.  From this
location, a 5/8" hose would be attached to the left side of this hose assembly and wrapped around toward the
passenger side valve cover.

We'll now focus on the passenger valve cover.  In the photo to the
right (and at the top of the page) you can see the modified oil fill cap.
The fitting in the top of the cap is a 3/8" NPT heater hose fitting.
These are found in the "Help" section.  The fitting differs from a
standard 3/8" NPT fitting in that the hose barb size is much larger
and doesn't neck down to fit the inner diameter of a 3/8" hose.
It flows straight through and fits the 5/8" hose.

Here's an example
comparison of the
two 3/8" fittings.

The two 90 deg fittings allowing the hose to loop downward are
again PCV hose connectors pieced together with 5/8" hose.  The
hose is too beefy to use as a direct push on and can potentially
interfere with the hood.   The loop required will sit too high.   As it
is, you'll need to cut your hose lengths with limited use space in
mind.  The line from the valve cover should be connected with a 'T'
into the line coming from the PCV valve location.  The remaining
port from this last 'T' is fed to the remote breather.  Place a
vacuum cap over the 3/8" hose nipple off the oil fill tube.

The Moroso breather I have has a single 3/8" NPT port on the side.
This fitting was also changed to a 3/8" NPT heater hose fitting.  

Without driver side valve cover modifications the install is complete.

I don't know if the next step was even necessary but I chose to do it to help balance any one sided pressures I had
in the engine.  In the below photos you can see where I ran a 3/8" hose from the passenger side valve cover oil fill
tube to my modified driver side valve cover.  The fitting in the driver side valve cover is once again a 90 deg PCV
connector and grommet, 5/8" hose, and a gutted PCV valve.  Measurements to drill this hole can be found on the Dual
PCV Valve page.  I still use this hole as my main oil fill hole due to relatively tight baffle clearances on the passenger
side cover.

Follow up: I have about 2000 miles on the engine with this setup.  The vehicle seems to run smoother than with the
3/8" system.  I have no oil being pushed out at the oil fill cap or on the driver side vent (no mess on the engine).  If I
start and stop the engine with very little drive time, I get a quantity of water built up in the catch can, but very little
obvious oil.  (The engine isn't fully warmed up and I'm catching the water condensation).  I have to say that so far,
this is the best set up for my supercharged engine where I know it's getting the venting that it needs.
Mustang Parts and Tech
Engine Breathers and Deleting the PCV System (5/8" Line)
Videos showing the draining and consistency of the fluid.
See videos of the end result at the bottom of the page.