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PCV Catch Can clarification


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So i was reading up on some old posts Mr. P wrote up about the PCV function and how to properly set up a catch can so your entire pcv system is actually functioning correctly. Well the post was from 2010 lol and I was curious if how I am about to write this is the correct way to vent a NA motor.

 

From drivers side valve cover pcv hose to top of catch can. Return line to top of intake manifold pcv nipple.

Passenger side breather on oil cap and cap the line at the valve cover going to the throttle body as well as the throttle body pcv nipple ( from PS valve cover)

 

This makes the most sense to me but I have not seen anyone with a lq9 run it this way. I have seen gto's do this which leads me to the belief that I am going crazy. My tuner also told me to run only off the DS and leave the passenger side alone. (No Breather, dont cap anything)

 

WHO IS RIGHT AND WHO IS WRONG?

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EDIT: i just reread your original post- the way your tuner said to run, if i read your post right- he is saying to leave the passenger side stock (pass. valve cover to intake tube/throttle) and take the driver side (from driver valve cover to manifold) and put a catch can inbetween, correct? if this is how he is telling you to run it on an NA setup thats stock/bolt-ons, this is ALSO correct. it isnt until boost or higher power levels that a breather / deleting pass. side OE setup is neccesarry. what is important to know- NEVER block off the PCV and JUST run a breather- that will cause serious issues down the road

 

Mr. P knew his stuff, its a shame he isnt around anymore. the first way you said to run a CC, is correct. for an NA setup, you should run a CC between the driver side valve cover and the intake manifold. if your car/truck still has the PCV inlet on the valley, under the throttle, your going to run a line from the valley and T it into the line BEFORE the catch can, coming from the driver valve cover. this way you can evacuate the crankcase gases even more effiecently. NOW that we have the evacuation covered, we need to get the fresh air in, to push the old air out towards the CC and manifold. SO you have two choices- you can either: run a second CC between the passanger valve cover and the intake tube OR you can run a ONE WAY valve breather cap (revxtreme.com) on the passanger valve cover and cap off the intake tube and the pass. valve cover. the only issue with running the breather is you need to retune your PCM (you dont HAVE to but it will throw your fuel trims off a bit) becuase your PCV is hooked from the driver valve cover to the manifold, and you have a breather on the passanger side- this is basically a small vaccumn leak that runs air through the engine and into the manifold, AROUND the MAF causing the PCM not to measure it. as long as you have under say 650 WHP or under 10-12 psi boost, you can use the setup mentioned above. running the dual catch cans WITHOUT a breather is just fine if you dont have the ability to retune easily.

 

if anyone has any questions about PCV setups or anything like this, please feel free to give me a shout- PM, text, whatever. your PCV system is VERY important to your engines longevity, HP, and in preventing gasket leaks (boosted engines mostly). i would like to make a thread on PCV setups for every type of engine setup, if we can get it sticky'd that would be helpful as i have posted in over 4 PCV questions threads just this week.

Edited by kelleyperformance (see edit history)
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yesss! the exact answer I was looking for. Now if i was to have say my cam and a set of 243's making around 400 maby a tad more. and say I shoved a 200 shot down its throat would this come into consideration regarding PCV when a breather is needed? also regarding pcv is this why people switch to the ls6 valley or ls2 valley where it pulls from the valley cover instead of the DS valvecover

?

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i have 2 catch cans. one on the clean side because ive heard that if you are revving it real high often the oil can build up and come back through the clean side. I also have one on the dirty side too

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  • 2 weeks later...

Ive got a supercharged 370 build coming together this weekend and am going to order a can. ill have lots of questions for kellyperformance. :cool:

give me a call or text :thumbs:

yesss! the exact answer I was looking for. Now if i was to have say my cam and a set of 243's making around 400 maby a tad more. and say I shoved a 200 shot down its throat would this come into consideration regarding PCV when a breather is needed? also regarding pcv is this why people switch to the ls6 valley or ls2 valley where it pulls from the valley cover instead of the DS valvecover

?

sorry i just now saw this... new topics didnt catch this. the newer valley PCV works much better, but it isnt really worth the work to change it out unless you already have it off for some reason. if you run how i described above, you will be just fine. as to the N20, it wont be any issue regarding PCV, either use a one-way breather or a CC on the fresh air side

i have 2 catch cans. one on the clean side because ive heard that if you are revving it real high often the oil can build up and come back through the clean side. I also have one on the dirty side too

this is true, if you keep the clean side run like OEM, higher output/boosted motors can suck oil right out of the clean side through the throttle :banghead:

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I need to start planning on PCV and catch can mods for my truck in the near future as well...any advice kelleyperformance? Mods are in sig...currently running stock PCV setup with 8-10lbs of boost...want to get some ideas...

 

EDIT: kelleyperformance...found your post in the other thread...will go from there...

Edited by GreenMtnSS (see edit history)
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Okay, here's one for ya. My mods are in my sig. My LS3 TB doesn't have a passenger side breather like my stock one did. I ran my drivers side to a T then the passenger side to the T then the open end to the top of the manifold. I know this is NOT good, so should I just run the drivers side to the top of the manifold like the general intended and then cap the passenger side and have a breather instead of a oil cap???

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I need to start planning on PCV and catch can mods for my truck in the near future as well...any advice kelleyperformance? Mods are in sig...currently running stock PCV setup with 8-10lbs of boost...want to get some ideas...

 

EDIT: kelleyperformance...found your post in the other thread...will go from there...

run it like described above, will work well. let me know if you need anything

Edited by kelleyperformance (see edit history)
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Okay, here's one for ya. My mods are in my sig. My LS3 TB doesn't have a passenger side breather like my stock one did. I ran my drivers side to a T then the passenger side to the T then the open end to the top of the manifold. I know this is NOT good, so should I just run the drivers side to the top of the manifold like the general intended and then cap the passenger side and have a breather instead of a oil cap???

you shouldve run the passenger side to either the intake tube, or vent to atmosphere. one side (right) should be pulling fresh air in, not have suction/pressure; the left side, or valley cover, should be running from the cover-to a catch can-to vaccum port on the manifold. and you should run either the RX catch can that has a built in valve or a PCV valve in line between the manifold and CC. the current way you descirbed is not good, as there is some evacuation of crank case gases but no source of fresh air to push the bad air through and out of the engine.

Edited by kelleyperformance (see edit history)
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you shouldve run the passenger side to either the intake tube, or vent to atmosphere. one side (right) should be pulling fresh air in, not have suction/pressure; the left side, or valley cover, should be running from the cover-to a catch can-to vaccum port on the manifold. and you should run either the RX catch can that has a built in valve or a PCV valve in line between the manifold and CC. the current way you descirbed is not good, as there is some evacuation of crank case gases but no source of fresh air to push the bad air through and out of the engine.

 

Yes, I realized I was just creating a total vacuum with T-ing everything and preventing fresh air. But just venting the passenger side would induce contamination because that's the "intake" side, no? Why exactly couldnt I just cap it and put a breather on where the oil cap is? At least that way there will be some filtration. I'm not knocking your methods, just looking for some answers.

 

*Although if I drill a hole in my CAI and run the hose from the passenger side valve cover that would be filtered... It would just suck to have to do that.

Edited by canadianVRss (see edit history)
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Yes, I realized I was just creating a total vacuum with T-ing everything and preventing fresh air. But just venting the passenger side would induce contamination because that's the "intake" side, no? Why exactly couldnt I just cap it and put a breather on where the oil cap is? At least that way there will be some filtration. I'm not knocking your methods, just looking for some answers.

 

*Although if I drill a hole in my CAI and run the hose from the passenger side valve cover that would be filtered... It would just suck to have to do that.

yeah thats why the intake tube works well, but sometimes on higher HP builds some light suction through the throttle body can pull oil through. so you can run a filter on the oil cap, but i would only use one with a built-in check valve that only lets air IN not out. you can find that at revxtreme.com (RX), they have check valve oil caps (use TBSS as application, they dont list SSS)

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yeah thats why the intake tube works well, but sometimes on higher HP builds some light suction through the throttle body can pull oil through. so you can run a filter on the oil cap, but i would only use one with a built-in check valve that only lets air IN not out. you can find that at revxtreme.com (RX), they have check valve oil caps (use TBSS as application, they dont list SSS)

 

Awesome thanks man I'll take a look right now.

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