89frankenford said:

are you saying that both banks need a bailout?? lol



i know i know REALLY bad joke

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Sometimes the bad ones are the best!!!

mrfixit said:

That's fine, Chris. I can understand.
But take a hard look at what it does- it is there to recycle blow-by into the intake so that vapors are burned off. That is why you had that oily scum you mentioned. It pulls blowby off of the right bank, and the pcv typically handles the left bank.

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I understand the idea behind the system Tom, but I don't believe that you need a vent on each bank of cylinders. There is only 1 giant sealed oil chamber-- not 2 separate chambers. Any vapors in one back are now airborn and free to move between the two banks. It would make the most sense for the engine to have a system which pulls fuel vapors from 1 bank and displace the vapors with fresh air in the opposing bank. This would ensure that you have a flow of fresh air from 1 bank to the other, as opposed to having both intake and discharge on the same valve cover-- the other bank could remain with stagnant fuel vapors never getting cycled out.

So clearly one of the lines is for exhaling fuel vapors and recycling them back into the intake, and the other line is for displacing those fuel vapors with fresh air in the crankcase to prevent it from pressurizing (yes it's a sealed system, or it damn well BETTER be!!).

The only thing that I'm not entirely sure about is just exactly which line is intake and which is exhale. I'll see if I can do some digging in my Ford manual to find out.

Keep digging-
the blowby on the right is the passive system, with the cap being the regulator. The PCV is an Active system, to provide (surprise!) Positive Crankcase Ventilation, or PCV for short.
Yes, it's a sealed system, but there's plenty of extra "air" supplied in what manages to seep past the rings, etc. and the system is designed to normalize pressure in more than one way. If the PCV valve fails, that pressure needs to go somewhere, right? That's the first thing to check when you have that sludge you spoke of, the PCV valve.
if the hose were to be drawing air IN while the motor runs, the intake vacuum would negate the system, especially under load.
Also, the banks I spoke of were referring to TWO heads, with two valve
covers. in a high-flow oil condition, all the ports and passages have the potential to do a kind of "Vapor-lock" restricting incoming oil flow, just like if you put a five-gallon bucket over your head and lowered yourself into the swimming pool- air is trapped, so you can breathe, for a while, anyway.
If the system did as you suggest, oil flow would even be diminished, since the air would be "pulling" from the right valve cover, under the plenum thru to the left valve cover.

Skandocious said:

Did we ever figure out just why in the world we've got the PCV (positive crankcase ventilation) and yet we still need to have this breather tube that makes a mess in my intake?

My truck is not like some of those where it goes to the airbox and has a fancy little filter. No sir-- direct from the factory the tube connects direct from the filler neck to the middle of my intake duct, about 12 inches from my throttle body I peered inside the other day when I was doing my sag pump swap and it was all slimy inside I'd sure like to cap it completely if it serves the same purpose as the PCV. Dumping it into the engine compartment somewhere is not an option for me.

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Mine too, it just sucks from the other side of the passenger side wheel well from a tube thats stuffed down there, that goes into the coffee can to the motor....

http://en.wikipedia.org/wiki/PCV_valve

Wikipedia said:

The PCV valve is only one part of the PCV system, which is essentially a variable and calibrated air leak, whereby the engine returns its crankcase combustion gases. Instead of the gases being vented to the atmosphere, gases are fed back into the intake manifold, to re-enter the combustion chamber as part of a fresh charge of air and fuel. The PCV system is not a classical "vacuum leak." All the air collected by the air cleaner (and metered by the mass air flow sensor, on a fuel injected engine) goes through the intake manifold. The PCV system just diverts a small percentage of this air via the breather to the crankcase before allowing it to be drawn back in to the intake tract again. It is an "open system" in that fresh exterior air is continuously used to flush contaminants from the crankcase and into the combustion chamber.

The system relies on the fact that, while the engine is running, the intake manifold's air pressure is always less than crankcase air pressure. The lower pressure of the intake manifold draws air towards it, pulling air from the breather through the crankcase (where it dilutes and mixes with combustion gases), through the PCV valve, and into the intake manifold.

The PCV system consists of the breather tube and the PCV valve. The breather tube connects the crankcase to a clean source of fresh air, such as the air cleaner body. Usually, clean air from the air cleaner flows in to this tube and in to the engine after passing through a screen, baffle, or other simple system to arrest a flame front, to prevent a potentially explosive atmosphere within the engine crank case from being ignited from a back-fire in to the intake manifold. The baffle, filter, or screen also traps oil mist, and keeps it inside the engine.

Once inside the engine, the air circulates around the interior of the engine, picking up and clearing away combustion byproduct gases, including a large amount of water vapor, then exits through a simple baffle, screen or mesh to trap oil droplets before being drawn out through the PCV valve, and into the intake manifold.

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That article confirms everything that I said... The hose that you've got dangling in the coffee can (Tom) is the breather hose and your engine is drawing air IN through that hose, into your crankcase to displace the vapors that is being drawn OUT by the PCV, which circulates the vapors into the intake manifold.

Anybody can write a wiki.

mrfixit said:

Anybody can write a wiki.

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Oh cmon don't use that defense, it's just an easy out for people who are trying to prove their point. Anyone who sits down to write a damned article about it must KNOW something. At least more than you and I. I don't see you feeling the need to write tech articles about how PCV systems operate, no, because you're not an expert and nor am I.

And even if the author WAS wrong, at least one of these 121 revisions would have corrected any of the wildly inaccurate portions:
http://en.wikipedia.org/w/index.php?title=PCV_valve&limit=500&action=history

I thought I qualifed my position defense in the beginning. I have mine, and the hose puts OUT pressure. Maybe excess blow-by, I don't know. All I have to react on is the evidence, and I DO NOT have another one to check against it.

Well I'm not going to argue anymore. I just wanted to ensure that whoever reads this thread has the right information at hand so they can decide for themselves whether or not it's a good idea to delete the hose and follow your halfass'd coffee can method...

Again, the reason I DO the Halfskank coffee can method is BECAUSE it was lining the air box and TPS with an oil film. That "method" has now saved countless TPS cleanings.

mrfixit said:

Again, the reason I DO the Halfskank coffee can method is BECAUSE it was lining the air box and TPS with an oil film. That "method" has now saved countless TPS cleanings.

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I've never had to clean my TPS and it works fine, best I can tell. If you were vigilant about putting new filters on the breather then you wouldn't have had that problem.

Spoken faithfully like someone who isn't here.

My tube isn't BEFORE the air filter anyway, so it's been sucking in 'dirty' air for the duration of its life. Air cleaners are great, but running without them isn't completely dangerous.

Ryan

O'Rattlecan said:

My tube isn't BEFORE the air filter anyway, so it's been sucking in 'dirty' air for the duration of its life. Air cleaners are great, but running without them isn't completely dangerous.

Ryan

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There is supposed to be a small filter on the breather:

I think chris should be banned for recommending we use a GM part...

It was a representative picture

Yeah... representative of injecting sodium silicate into your motor...

Chris is VERY close in his description.

If you have a WORKING PCV, there SHOULD be a vacuum on that hose. If the small filter (similar to the one in the picture) is getting oily, one of two things is happening. The PCV valve or line is stopped up, OR, you have so much blow-by the PCV can't keep up. Blow-by can be caused by worn rings, worn valve guides, or even a leaky head gasket. It isn't fuel vapors that is supposed to remove, but OIL vapors. That tube is a fresh air inlet for the block. Without it, say plugging it, you will pull a horrendous vacuum on the block, and probably promote premature failure of numerous gaskets and seals on the engine. Assuming the PCV is NOT stopped up, not having the filter on there will certainly pull in dirty air. If all you do is highway/city driving, probably not a huge issue, but Ford put that there for a reason. If you live in a rural area and spend much time on dirt roads, however, BIG PROBLEM. You may as well put a shovel full of dirt in when you change your oil.

All that said, the PCV system on the 5.0 has a built-in "defect" in that it goes into the back end of the intake. This is NOT good for #4 and #8 cylinders, which tend to hog most of the vapor from the crankcase, and run lean due to displaced fuel. If blow-by is serious enough, the vapors will cause the compression rings to sieze, and next thing is a scored cylinder wall. This is a COMMON failure of the 5.0. There is a mod for this that involves relocating the hose from the PCV valve to the back of the plenum to route it to the center of the plenum. This promotes sharing the block gasses with ALL the cylinders.

You are essentially pulling FULL intake vacuum on your crank case via the PCV. IF the airflow is excessive, or if liquid enters the PCV valve, it is designed to shut flow off. Let's say you're going up an extremely steep incline running relatively high RPM's. The oil may not drain properly from the valve covers, and will build in the back end of the covers. Guess where the PCV is on the 5.0. Gotta stop raw oil from going into the intake somehow, thus the little rattling valve in the PCV.

It was originally put on to improve emissions on cars dating back to the early 60's, and to prevent the oily vapors from contaminating the roadways and the cars. The PCV (Positive Crankcase Ventilation) system serves two purposes. 1.) Recover/burn vapors from the crankcase. 2.) Provide a partial vacuum on the block to improve oil consumption. Without that vacuum, the oil use will go way up, either by leakage, or via the valve guides. If you look at a new valve guide, it is (or should be)knurled inside to promote lubrication of the stem. Knurled = leaky. Lubricated, but leaky.

You don't have to have the tube in the air filter box, but you certainly do NOT want to block it, and you should prefer the air going IN that hole to be filtered. It IS an inlet to vent the vacuum created by the PCV connected to the plenum. If you're getting excessive vapors OUT of that hose, chances are you've got excessive blow-by or a stuck PCV valve. If the PCV valve is not stuck and has good vacuum on it, then it's time to check compression. If you suck air out of the block, some air has to go back in to VENTILATE the block as PCV was designed for. Older engines just had a breather cap. Some race engine builders that build big blocks actually add vacuum pumps to replace the PCV and capture the vapors in a reservoir rather than have PCV vapors screwing with the science they put into their air/fuel mix. I recently looked at a '68 Firebird with a 540 something big block in it. The guy that built it explained his vacuum pump to me. Made perfect sense.

Thank you Tim, that was very informative

Many many engines of this age DO have excessive blow-by; This was my original point...