I'm going to start this article tonight. I'm typing as this all comes to me. THEN i'm going to go back, edit it, and add pics. SO bare with me. PCV systems PCV stands for "Postive Crankcase Ventilation." Alot of people misunderstand the benefits of a properly functioning PCV setup on their cars. Some see oil in the intake and IMMEDIATELY blame the PCV system and begin to eliminate it all together. This is NOT always the best solution. Below is a VERY basic diagram on how the FACTORY PCV system works on a 94-95 5.0. It consists of a PCV Valve (located in the backside of the lower intake), and various vaccum lines. What purpose does it serve on MY motor? The word "Postitve" in "Positive Crankcase ventilation should be replaced with "Active" in my opinion. It makes more sense in MY mind. The reason I say that is b/c in a properly set up PCV, the crankcase itself isn't just pushing out pressure but its actually being "scavenged" or "drawn upon" but the intake, via the PCV Valve. This beats the "old school" breather setups, especially during part throttle (intake under vaccum) situations. Picture two jars side by side. Both filled with smoke (relates to crankcase fumes and pressure). Open BOTH jars. Take a vaccum to one jar and leave the other one open to the atmosphere....which one clears out most effectively and quickly? This is how a PCV system benefits....BUT they have to be setup properly! Two things in the crankcase that a PCV helps eliminate are 1) The most common problem PRESSURE! and 2) Detergents and Toxic fumes. Pressure in the crankcase is bad for MANY reasons. It slows down pistons on their downward travel during the intake and power strokes, negatively affects the sealing of piston rings to the cylinder walls, and can blow out seals and gaskets on the motor itself. Fumes in the crankcase are bad for the enviroment but also can act as solvents and begin to break down oil in the crankcase, leaving your internals less protected! SO how does it work exactly? Its kind of hard to draw out so I'll explain it from the PCV valve forward. Your PCV is mounted in the backside of the lower intake. The hole it is mounted in, leads to the lifter valley (Keep this in mind...the Lifter valley shares the SAME volume of air/gases as the crankcase and area under the valvcovers! Crankcase pressure is in ALL these areas! IT IS ALL THE SAME AREA! I'll explain why this is red later.) It is this area that must be vented! The PCV is connected to the upper intake plenum via a large vaccum line. It is HERE where the ventilation takes place! The engine, when running, is sucking on this hose...hence vaccum line...which draws on the crankcase! VOILA! POSITIVE VENTILATION! BUT WAIT! In order to ventilate...you have to MOVE air...not just creat a vaccum! PAY ATTENTION! This is where ALOT of Mustang owners screw up! Remember that little black hose from your oil filler neck to your intake tract that you probably tossed in the trash and replaced with a breather? Do you REALLY know why that leads into the intake tract? Many of you would say "Because of the that pesky EPA and their stupid emissions!" WRONG!!!! Think of the crankcase as your musty ass bedroom after you haven't done laundry for a month! Opening the door and putting a fan there is good...but you can move MORE air ACROSS the room if you open the window and have the fan DRAW IN FRESH AIR from outside across your stankin' room and out the door! A PCV works on the SAME principal! Makes sense now huh? Now you're probably saying "Well, the breather does that just fine!" Yeah it does...BUT you also just created a vaccum leak! Meaning your engine is now ingesting UNMETERED (Air that has NOT been measure by the MAF). THIS CAN CAUSE THE DREADED IDLE SURGE QUICKER THAN YOU CAN SAY "PVC." Now I've seen some cars, my own included where this wasn't an issue, BUT I've also seen it wreak havoc! How are you drawing unmetered air you ask? Well...but pulling off that little black hose and tossing it for a breather on your oil neck because you think it looks "trick" next to your cold air, you opened that neck up to the atmosphere...where before if was drawing on metered air from the intake after the MAF. This newly unmetered air travels down the neck, into the valve cover area, down to the lifter valley, up the PCV valve, and on in to the intake to wreak havoc on your idle. (Remember the red text above? That is why I wanted you to understand how the crankcase is one big open area). THAT is how the stock PCV works and WHY it is setup the way it is.... Ok so we know how it works. What is wrong with it? Well for starters...the #1 complaint you'll hear is "There is oil in my intake!!! HOW DID IT GET THERE?!" People hear "PCV" and flip and yank it all off. How does the oil get in the intake? Well, all those moving parts in the engine can REALLY get moving and splashing oil around. Those splashes make "oil mist." Its the mist that gets sucked up through the PCV and puts a nice coating on your intake. Now if you have a poweradder, or a higer milage motor, you generate more blowby and there for push MORE oil into the intake. ALSO, what can happen is HIGH RPMs with HIGH vaccum (i.e. you just made a 1/4mile pass and are at 5,000RPMS in 4th gear and snap the throttle shut and let the motor slow you down or "compression brake"). This generates EXTREMELY large amounts of vaccum in the intake as the motor is still spinning VERY fast but trying to suck against a closed throttle body so something has to give....alot of oil mist from the crankcase is what comes in. I personally, never down shift unless I'm corner carving. At the end of my runs, I throw it in neutral and let those things on each wheel that are designed to slow you down do their jobs. Thats me. Now, I had an 02 Lightning for a little under a year and ask ANY 2nd Gen. Lightning owner about oil in their intake and they can tell you a story for sure. They were EXTREMELY prone to it as the engine AND blower would suck LARGE amounts of oil from the passenger side cam. Well, owning that lightning taught me two things....1) How to get rid of it and 2) what it does to your motor. After doing LOTS of reading, I learned that oil mist can actually LOWER the octane of your fuel...but I don't see this as being TOO much a problem b/c I never ONCE read about a lightning owner blowing his or her motor due to oil in the intake causing detonation. As delicate as lightning motors were, I think Ford would have definetly recalled a truck or two if such were the case. How do you get rid of it? SEPERATE IT! After I bought my Lightning I realized that I too had ALOT of oil in my intake. I read about 50 million different ways to eliminate it. Alot of them were buying kits from reputable manufacturers (steeda, lightning force performance, etc). MANY shunned what I'm about to tell you but I tell you right now....Look at the picture of a $60 steeda oil seperator kit...and look at my $30 Home Depot setup. You be the judge.... $70 STEEDA $10 @ lowes + whatever you spend on the 3/8" Barbed fittings and vaccuum line.. I put the cheap-o setup on my oil swilling lightning and what do you know! My intake was dry as a bone the rest of the time I owned the truck! You can also see it work. Check it whenever you fill up on gas and just drain the bowl back into the oil. This setup of would go in the line between the PCV Valve and the port on the lower intake. Just cut or extend or replace the factory hose with two pieces of hose and this in the middle. If you car is consuming an unnaturally large amount of oil though, you might have bigger problems Excessive blowby (i.e. your rings are taking a dump on you) can increase cylinder pressures and cause the excess oil in the intake. A seperator is not a band aid for this.... THE OTHER bad thing about the factory PCV is that it is TOO SMALL! Its only 3/8" in diameter. I've got a 331 stroker that I turn to 6500 and spray with 150-175 shot of nitrous. My compression is GREAT BUT I build so much crankcase pressure that it overwhelms the stock setup and I would come back from a run and find my dip stick sticking half way out of the tube! This can also be the cased for Turbo/Supercharged cars where they actually pressurize the intake which inturn, tries to close the PCV valve (which is a one way valve, remember?) so it will slow down the process of scavenging the crankcase ALOT. Solution? Ditch the PCV setup. On my personal car....neither my intake (Victor 5.0) nor my valvecovers (JEGS custom cut) have provisions for PCV so it was a no brainer. HOWEVER, on your stock or close to stock car, you have to plug the PCV Valve in the back of the intake! I would just cap off the valve itself with a vaccum cap. Now, you can just cut a couple of holes in each valve cover and use some "push in" style breathers from pretty much ANY parts store! I would make sure to run atleast two (one on each) to allow adequate ventillation. The biggest CON to doing this is the same as a stock PCV Setup....OIL MIST! While it isn't in your intake this time, it can make its way down onto the valvecover...and if bad enough the headers making for a fire hazard. For this reason they sell baffled breathers and catch cans. Catch cans operate in much the same way the steeda seperator kit above does...just on a larger scale. You can find them at summit, jegs, and ESPECIALLY on eBay. After looking at the construction of one...I elected to make my own. I use two 3/4" fittings tapped into the back of each valvecover and then they merge into a 1" piece of braided pvc tubing...into my "homemade" vented catch can. The can is filled with steel wool. The wool acts as a filter...catching all the mist on the strands. Eventually the oil puddles at the bottom of the can. Thats where the size 6an drain comes in handy. There you have it. Thats the ins and outs of a pcv setup. Any add ons, questions or comments...FEEL FREE!!!