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1 pcv on each valve cover?

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Old 07-24-2017, 12:28 AM   #1
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1 pcv on each valve cover?

Hello, I'm new to this forum, anyways I'm not sure if I'm posting in the correct place. My question is, is it bad or what is occurring when there is a pcv on each valve cover? I know its supposed to be one non restrictive and the other with a pcv.... Any feedback would be appreciated....
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Old 07-24-2017, 08:39 AM   #2
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Re: 1 pcv on each valve cover?

If they are hooked up to the same spot, you'll create 2 much vacuum in the crankcase and may pull seals in. (no fresh air either)
If they are plumbed to the correct spots, you'll have vacuum in the crankcase but no fresh air coming in brecause of the way the valve works..
In short, you can gut a pcv valve to use for the fresh air line.
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Old 07-24-2017, 05:53 PM   #3
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Re: 1 pcv on each valve cover?

One PCV valve is sufficient. Some folks install a second one because the engine has excess blow-by (worn out) and they think they've "fixed" something.

Ditch the second PCV valve. Install an OEM-style filtered air inlet (usually a hose to the air cleaner, with a filter of some sort inside the air cleaner) in place of the add-on PCV valve, to return the system to proper functionality. If you have a properly-functioning PCV sysgtem, but still have excess blow-by, you'll need engine repair.
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Old 11-14-2017, 11:34 AM   #4
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Re: 1 pcv on each valve cover?

I hope I'm not too late to offer you better advice. Installing a second PCV on the opposite valve cover is a good idea. The engine will not "suck" in its gaskets. Putting a vacuum on the crankcase helps seal the piston rings. Keeping fresh air out of the engine also keeps out moisture which makes your oil last longer. No modern engine has a "fresh air" intake. There is lots of advice on this board... some good... some not so good
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Old 11-14-2017, 06:09 PM   #5
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Re: 1 pcv on each valve cover?

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Originally Posted by 1982Z28Modified View Post
I hope I'm not too late to offer you better advice. Installing a second PCV on the opposite valve cover is a good idea. The engine will not "suck" in its gaskets. Putting a vacuum on the crankcase helps seal the piston rings. Keeping fresh air out of the engine also keeps out moisture which makes your oil last longer. No modern engine has a "fresh air" intake.
Define "modern engine". The engine we're dealing within this thread was engineered to have a fresh-air inlet to the crankcase, which does double-duty as a fume vent when the PCV valve is overloaded by excess blow-by.

The PCV system--even with two of them--is not going to generate enough vacuum to improve ring sealing the way a race-engine vacuum pump does. The point being that the engine the OP is posting about likely has SO MUCH BLOWBY that it needs repair, not a damned Band-Aid in the form of a second PCV valve. Other possibilities are that the previous owner was simply an outright idiot, or that one of the PCV valves was defective, and the previous owner thought a second one was a good idea...which is still borderline idiot.

Keeping fresh air out of the engine DOES NOT keep out moisture, the moisture comes from the combustion byproducts that are blowing past the rings. The engine is making it's own moisture--which is why exhaust is all white and steamy in cold weather. When exhaust gets past the rings, the moisture in it contaminates the oil. This is why the first thing we need to know is "does the engine have excess blow-by?" (All engines have some blow-by, which is what the PCV/fresh air intake is designed to compensate for.)


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There is lots of advice on this board... some good... some not so good
Oh, God...how true. And the irony is making me smile.
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Old 11-14-2017, 06:31 PM   #6
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Re: 1 pcv on each valve cover?

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There is lots of advice on this board... some good... some not so good
Guess which bucket you fall in today....
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Old 11-14-2017, 06:50 PM   #7
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Re: 1 pcv on each valve cover?

ALL modern engines have fresh air into the crankcase.

That's, ALL. Since the mid 60s in CA and the late 60s in the other 49. Not sure if that counts as "modern", but ...

Engines with a MAF have their fresh air inlet behind the MAF and in front of the throttle blade; my truck (LM7 / LQ9) are that way. PCV out of the driver's side VC and into the plenum behind the TB, and fresh makeup air into the pass side VC from behind the MAF at the front of the TB.

The ONLY WAY PCV can work, is by circulating air through the motor, to allow foul air in the crankcase to be drawn into the intake and get burned.

Correct PCV routing in a non-MAF setup, such as TBI, is the PCV valve on one VC connected to hard manifold vacuum drawing the nasty vapors OUT and into the intake, and fresh clean filtered air coming IN on the other.

I agree, it's usually not too hard to tell which kind of "advice" is which, if you're experienced. The problem comes when a novice gets told what he wants to hear instead of what's TRUE, and has no way to recognize the error.
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Old 11-14-2017, 07:20 PM   #8
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Re: 1 pcv on each valve cover?

Quote:
Originally Posted by Jose Leon View Post
My question is, is it bad or what is occurring when there is a pcv on each valve cover? I know its supposed to be one non restrictive and the other with a pcv.... Any feedback would be appreciated....
Air travels from high pressure to low pressure. You want to create a path of air flow from "clean air inlet" (high pressure) ---> "intake manifold" (low pressure). The "clean air inlet" is at one valve cover, and the PCV valve is on the other valve cover and plumbed to the vacuum side of the intake manifold. The intention is to create a cross-flow that helps evacuate the crankcase.

In your case you simply have two valves that vent to atmosphere when the crankcase becomes pressurized. It is not actively evacuating the crankcase like you want to happen.

The "clean air inlet" is sourced from any filtered air supply at ambient pressure (wherever it is most convenient). You can grab it from an air port somewhere in front of the throttle blade. That can be an intake tract, or a port on the throttle body, or if neither is available then just a plain old air filter right on top of the valve cover. It is a little more environmentally responsible to grab the the clean air from the engine intake tract so that any crankcase vapors that escape are burned by the engine.
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Old 11-14-2017, 09:04 PM   #9
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Re: 1 pcv on each valve cover?

the pre eminent prima donnas have spoken. I must be wrong. Not quite.
I believe none of you are Master Mechanics. I am. Just because you have posted 19,000 times doesn't make your advice any better than mine.

As far as sofa goes... fresh air is no longer pulled into the crankcase... it was at one time. Remember that dirty oily filter in you 3rd gens air cleaner? that is caused by the crankcase gases flowing up the hose and soaking that filter.

So shurkey, QWK, and sofa can all bite me. Which one of you is the Master Mechanic?

Jose... this is why i sent you a PM. These *******s would rather go on and on about how there right and your wrong, but not offer any good advice.
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Old 11-14-2017, 09:28 PM   #10
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Re: 1 pcv on each valve cover?

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Old 11-14-2017, 09:51 PM   #11
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Re: 1 pcv on each valve cover?

Quote:
fresh air is no longer pulled into the crankcase
You're as full of excrement as a Christmas turkey.

Go out and LOOK AT a car. Or a truck. Any highway-rated vehicle will do. I used my 20xx truck examples as a "modern" case in point (LSx) engines. Go FIND ONE where what you claim is true. Go ahead, I DARE YOU.

José, ignore that guy. He doesn't know what he's talking about. He's a perfect example of the BAD "advice" you can get here. (or really, just about anywhere on the Internet) And likewise, why I NEVER EVER EVER take my cars to a "mechanic", "master" or any other kind, except as an ABSOLUTE LAST RESORT, since getting a sticker for their uniform seems to puff up some of their ego to where they think they can IGNORE the evidence of the thing sitting right in front of their eyes. Unfortunately the worst thing about the Internet is, it allows ignorant or ill-intentioned or otherwise unsuitable people, to pretend to appear just as useful as people who actually know what they're talking about and want to help out the beginners. Too bad you have one interfering with your honest quest for actual knowledge.

Quote:
Just because you have posted 19,000 times doesn't make your advice any better than mine.
No indeed, it doesn't, you're quite right about that. What makes my advice better than yours is, I KNOW what I'm talking about, and you DON'T.
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Old 11-14-2017, 10:04 PM   #12
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Re: 1 pcv on each valve cover?

OK, so just for the halibut, I snapped you guyz acoupla pics of a LQ9 I bought the other day.

Whaddya think?

PCV valve in driver's side valve cover, and makeup air in the pass side one. The makeup air in this application, since it has to be downstream of the MAF, comes off of the TB, such that the air is cleaned and filtered by the main air cleaner; whereas in a TBI car, with no MAF, the makeup air comes through the little filter in the air cleaner.

José, plumb your car somewhat like this. One PCV valve, one clean filtered makeup air port.
Attached Thumbnails
1 pcv on each valve cover?-lq9-pcv-drivers-side   1 pcv on each valve cover?-lq9-pcv-pass-side  
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Old 11-14-2017, 11:48 PM   #13
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Re: 1 pcv on each valve cover?

What a clown. Loud and proud, vehemently arguing he is correct, but too scared to explain or put anything in writing for fear that others will critique.

Jose Leon, if you cut and paste that PM here then you won't need to guess what advice to follow as I am certain it can be hashed out very quickly.
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Old 11-14-2017, 11:59 PM   #14
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Re: 1 pcv on each valve cover?

Ummmm, I worked on a Volvo the other day Mr.Master mechanic can't recall exactly what year but it was fairly new. The cel was on on my snap on scanner pulled a code P052e. Since you are a master mechanic you should know what this code indicates. So tell me does this engine not ventilate the crankcase?
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Old 11-15-2017, 08:18 AM   #15
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Re: 1 pcv on each valve cover?

Wow, I'm thinking the "master" may need a refresher course.
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Old 11-15-2017, 09:10 AM   #16
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Re: 1 pcv on each valve cover?

Mr. "Master Mechanic",

I sure hope they didn't teach you "more is better" in school. More is not always better, in fact, with engines, it's usually worse. The RIGHT amount of things- fuel, timing, coolant, vacuum, oil, etc is BEST. Too much oil, fuel, timing, is not.

More vacuum in the crankcase is not better. The RIGHT amount of vacuum is the best. A CORRECTLY running PCV is BEST.

A CORRECTLY running engine is best.

And with enough vacuum, you sure can pull a lot of things into an engine.
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Old 11-15-2017, 11:10 AM   #17
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Re: 1 pcv on each valve cover?

Quote:
Originally Posted by 1982Z28Modified View Post
This troll sofa averages 4.5 posts a day for 12 years! Does he have a job? Other than trolling this website? Moms basement for sofa!
Sometimes it's called multitasking. Some of us work behind a desk 8hrs a day, and between more intensive tasks, we participate on the forum. Some of us enjoy the community, and try to give back when we can to return the favor.

Some of us like to hang out for the entertainment, reading some of the stupid things inevitably posted.
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Old 11-15-2017, 11:19 AM   #18
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Re: 1 pcv on each valve cover?

"Sometimes it's called multitasking. Some of us work behind a desk 8hrs a day, and between more intensive tasks, we participate on the forum. Some of us enjoy the community, and try to give back when we can to return the favor.

Some of us like to hang out for the entertainment, reading some of the stupid things inevitably posted."


Perfectly said, Drew!
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Old 11-16-2017, 10:03 AM   #19
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Re: 1 pcv on each valve cover?

Quote:
Originally Posted by 1982Z28Modified View Post


Why is it that NASCAR engine run with 20" of vacuum in the crankcase?


Answer that question smart guys.

We aren't talking about NASCAR engines that get freshened after every race but since you bring it up, it's for better ring seal with the sustained rpm they run.
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Old 11-16-2017, 10:21 AM   #20
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Re: 1 pcv on each valve cover?

Horsepower......And NASCAR engines are operating in excess of approximately 8300 RPM.

NASCAR engines, (unlike the majority on this site) have special crankshaft seals (front and rear) which have the sealing lips reversed to hold that higher level of vacuum to keep from blowing out the seals.

And BTW, I'm not looking for a pissing contest here. Your remarks above are uncalled for. You know very little about me. And what you DO know, you seen it in my info.
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Old 11-16-2017, 12:13 PM   #21
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Re: 1 pcv on each valve cover?

Quote:
Originally Posted by 1982Z28Modified View Post
I thought this type of website was designed for the free exchange of CORRECT ideas?
FIFY.

Quote:
Originally Posted by 1982Z28Modified View Post
Why is it that NASCAR engine run with 20" of vacuum in the crankcase?

Answer that question smart guys.
They aren't doing it with PCV valves.
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