PCV Question
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Teching In
Joined: Jan 2019
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From: Battle Ground, WA
PCV Question I've searched this and it seems Google is trying to find an answer... but not quite. So I'm thinking of running a catch can system. I have the later style valve cover with the built in valve on the drivers side. I have 2 questions here. 1. Should I run another PCV valve inline as added safety that I can easily replace? 2. Would it be a bad idea to run one with a breather and vent it to the atmosphere instead of returning it to the manifold? I don't see how venting it instead of running it back to the manifold will hurt performance, but I'd rather ask dumb questions and do this right the first time instead of coming here after my engine craps out...
You can run however many pcv valves you want. 1 is enough to do the job, if you want to add another it wont affect anything.
I personally prefer not venting to atmosphere, and if you run to atmosphere you don't need a catch can. The catch can works by vacuum being sucked through it and catches oil mist in the air. With venting to atmosphere, it's vented to atmosphere and not sucked back into the intake.
I personally prefer not venting to atmosphere, and if you run to atmosphere you don't need a catch can. The catch can works by vacuum being sucked through it and catches oil mist in the air. With venting to atmosphere, it's vented to atmosphere and not sucked back into the intake.
Thread Starter
Teching In
Joined: Jan 2019
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From: Battle Ground, WA
You can run however many pcv valves you want. 1 is enough to do the job, if you want to add another it wont affect anything.
I personally prefer not venting to atmosphere, and if you run to atmosphere you don't need a catch can. The catch can works by vacuum being sucked through it and catches oil mist in the air. With venting to atmosphere, it's vented to atmosphere and not sucked back into the intake.
I personally prefer not venting to atmosphere, and if you run to atmosphere you don't need a catch can. The catch can works by vacuum being sucked through it and catches oil mist in the air. With venting to atmosphere, it's vented to atmosphere and not sucked back into the intake.
No problem. You could always wait to see if it does fail and then put one inline, I have never seen one fail on a LS motor, and I'm a tech so I see a good bit of them.
Keeping the PCV active is great for the motor since it keeps a vacuum in the crankcase (reduces pumping losses aka increase in power), not to the extreme a vacuum pump will but it does help. It also sucks moisture out of the crank case and contaminants (fuel mist etc). If you vent to atmosphere you loose all those benefits. You may not ever notice the difference, but because of those reasons I like to keep the pcv active and not vent.
Also if you vent, you'll have to tune for it, it's currently tuned to account for airflow through the PCV, and it's a calculated amount so even changing the PCV can change things. I have that issue with Fords, they are super sensitive to the PCV flow rate. GM's seem to be a lot more lenient in that area.
Thread Starter
Teching In
Joined: Jan 2019
Posts: 13
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From: Battle Ground, WA
No problem. You could always wait to see if it does fail and then put one inline, I have never seen one fail on a LS motor, and I'm a tech so I see a good bit of them.
Keeping the PCV active is great for the motor since it keeps a vacuum in the crankcase (reduces pumping losses aka increase in power), not to the extreme a vacuum pump will but it does help. It also sucks moisture out of the crank case and contaminants (fuel mist etc). If you vent to atmosphere you loose all those benefits. You may not ever notice the difference, but because of those reasons I like to keep the pcv active and not vent.
Also if you vent, you'll have to tune for it, it's currently tuned to account for airflow through the PCV, and it's a calculated amount so even changing the PCV can change things. I have that issue with Fords, they are super sensitive to the PCV flow rate. GM's seem to be a lot more lenient in that area.
Keeping the PCV active is great for the motor since it keeps a vacuum in the crankcase (reduces pumping losses aka increase in power), not to the extreme a vacuum pump will but it does help. It also sucks moisture out of the crank case and contaminants (fuel mist etc). If you vent to atmosphere you loose all those benefits. You may not ever notice the difference, but because of those reasons I like to keep the pcv active and not vent.
Also if you vent, you'll have to tune for it, it's currently tuned to account for airflow through the PCV, and it's a calculated amount so even changing the PCV can change things. I have that issue with Fords, they are super sensitive to the PCV flow rate. GM's seem to be a lot more lenient in that area.
It's literally the easiest engine ever to work on in my opinion. I work on nissans too, not too much because they are great cars, but they are certainly more difficult than LS engines.
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Teching In
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From: Battle Ground, WA
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Pfft. Y'all think Nissans are bad? Nissans are simple.
Try German cars if you really want to throw your wrench down in anger.
Anyway, I was of the understanding that the PCV system on the O/P's engine didn't have a valve at all, that it was a "fixed orifice" PCV system. It's only a small hole in a plate inside the valve cover. From what I've read, GM found this design reduced oil consumption.
For my build, I just sprayed a bunch of carb cleaner through it and blew it out with some compressed air. We'll see how well it works once the car is running.
Try German cars if you really want to throw your wrench down in anger.
Anyway, I was of the understanding that the PCV system on the O/P's engine didn't have a valve at all, that it was a "fixed orifice" PCV system. It's only a small hole in a plate inside the valve cover. From what I've read, GM found this design reduced oil consumption.
For my build, I just sprayed a bunch of carb cleaner through it and blew it out with some compressed air. We'll see how well it works once the car is running.
Keeping the PCV active is great for the motor since it keeps a vacuum in the crankcase (reduces pumping losses aka increase in power), not to the extreme a vacuum pump will but it does help. It also sucks moisture out of the crank case and contaminants (fuel mist etc). If you vent to atmosphere you loose all those benefits. You may not ever notice the difference, but because of those reasons I like to keep the pcv active and not vent.
Nope
Pfft. Y'all think Nissans are bad? Nissans are simple.
Try German cars if you really want to throw your wrench down in anger.
Anyway, I was of the understanding that the PCV system on the O/P's engine didn't have a valve at all, that it was a "fixed orifice" PCV system. It's only a small hole in a plate inside the valve cover. From what I've read, GM found this design reduced oil consumption.
For my build, I just sprayed a bunch of carb cleaner through it and blew it out with some compressed air. We'll see how well it works once the car is running.
Try German cars if you really want to throw your wrench down in anger.
Anyway, I was of the understanding that the PCV system on the O/P's engine didn't have a valve at all, that it was a "fixed orifice" PCV system. It's only a small hole in a plate inside the valve cover. From what I've read, GM found this design reduced oil consumption.
For my build, I just sprayed a bunch of carb cleaner through it and blew it out with some compressed air. We'll see how well it works once the car is running.
Sorry but I have to disagree on the increase it power, PCV systems only work at idle and light throttle (vacuum) and do practically nothing when you're on the gas and under load. (No Vacuum) Plus you're contaminating the combustion process when using one. On an engine that is going to be used as a daily driver then the benefit is a cleaner engine and longer oil life. On a drag car or weekend only type cruiser the oil is usually changed more often and the motor isn't expected to last 100 thousand miles or more before it needs to be rebuilt so running a PCV system isn't a concern.
At light throttle, like you said, the pcv is active.. and you're making some power there. That's where we drive 99% of the time and there will be a small increase in efficiency there using the PCV system which does increase power by reducing parasitic loss which also equates to better MPG, if we want to get all technical about it lol.
It it is likely negligible, but on a street car keeping the PCV.. the benefits far outweigh removing it and running a vent.
I agree that they don't function at high throttle and do nothing for high/wide open throttle, but I also never said they did, and that's why I wrote "not to the extreme that a vacuum pump works". I didn't want to write a book on something we weren't even talking about. I was just speaking in general terms about keeping a vacuum system.
I agree with the rest you wrote though.
Last edited by 00pooterSS; May 13, 2019 at 02:58 PM.