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PCV valve question

This is a discussion on PCV valve question within the General Help forums, part of the LSx Technical Help Section category; This might a dumb question, but here goes: Is there a reason that the PCV valve connects to the intake ...

  1. #1

    PCV valve question

    This might a dumb question, but here goes:

    Is there a reason that the PCV valve connects to the intake manifold?

    I've read that people install a catch-can to filter out any residue oil, but would it be feasible to have the PCV valve connected to a modified engine oil filler cap (for example) instead?

    I can't help thinking that any oil should be fed back into the sump rather than the cylinders.


    As always, all knowledge eagerly received.


    Mike.

  2. #2
    Spaz is My Mentor SMWS6TA's Avatar
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    It purpose is to dump any oil that has by passed the PCV into the intake and let it be burned in the cylinders. Your idea would make some sense but it took several yrs for GM to catch their mistake with the LS1 PCV system to make a correction like the one on the LS6.

    have you checked out this thread?

    Explaination of OEM PCV vs LS6 VCT Mod



    It explains the differences between the LS1 vs LS6 PCV setups.

  3. #3
    Quote Originally Posted by SMWS6TA View Post
    It purpose is to dump any oil that has by passed the PCV into the intake and let it be burned in the cylinders. Your idea would make some sense but it took several yrs for GM to catch their mistake with the LS1 PCV system to make a correction like the one on the LS6.
    I'm horrified that a huge company, such as GM, could make the PCV system look like an afterthought.

    To use an expression from England; I'm gob-smacked.



    Quote Originally Posted by SMWS6TA View Post
    have you checked out this thread?

    Explaination of OEM PCV vs LS6 VCT Mod



    It explains the differences between the LS1 vs LS6 PCV setups.
    That's a very interesting thread, is removing the intake a simple or difficult job? It looks very tight for space when I look under my hood.

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    Member cowstandmoto's Avatar
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    Hey Mike. It does suck. Be ready to scratch up your hands and arms. One quick tip for you, should you go ahead and try those mod's; the last five (5) intake bolts closest to the firewall. I can't remember how they placed on the intake (like 3 on the passenger side and 2 on the driver side, or if it the reverse from what I'm describing) but those last 5 bolts you will need to take some 1/8" I.D. or 3/16" I.D. rubber hose, cut it in 1" long pieces, and then slit it length-wise the whole
    1" length on one side. And then when you lift those last 5 bolts you put one of those pieces of hose around the body of the bolt to elevate the bolt above. The reason you have to do this is because there is not enough room under the cowl to pull the bolts out of the intake.

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    The simplest solution is to install a catch can on the PCV system.


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    Spaz is My Mentor SMWS6TA's Avatar
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    Quote Originally Posted by SS Camaro UK View Post
    I'm horrified that a huge company, such as GM, could make the PCV system look like an afterthought.

    To use an expression from England; I'm gob-smacked.
    Really?!? I hope you were being sarcastic. That style of PCV has been around for many, many years. It really is not a complete POS, but the mistake that they made was putting it on the rear of the valve covers directly over where the oil is forced up to the valves. They used to have them at the front of the covers but for some reason it was moved to the rear on the LS1.


    Quote Originally Posted by SS Camaro UK View Post
    That's a very interesting thread, is removing the intake a simple or difficult job? It looks very tight for space when I look under my hood.
    Like I stated in the thread - this is not a performance mod and the LS6 VCT is cheaper part vs the OEM PCV. There is a thread in the tech stickies that gives very good directions. Total time for me to do this took about 2.5 hrs because I had to notch the block while in my driveway. I took my time and didn't rush. I would say that if you are planning on doing something else like replacing the knock sensors or OPSU, things that require you to remove the intake or are doing an intake swap (like going to a FAST 102) I would say wait to do this mod till you do them. Only because you have to do the same work and not have to do it twice. Or if you are like me and loath the OEM PCV setup, just removing the intake is not to difficult. You are lucky because you have a 02' - this means you will not need to notch the block like 98-01's have to make room for the LS6 VCT also you have the LS6 intake (this is a good intake, next better upgrade would be a FAST 90 or 102. 90's are hard to come by because they are no longer made and the 102 has more stuff needed then just the intake and cost $1k.

    I ended up doing this mod because after I did my intake swap I pinched the KS wire harness and had to go back and replace/upgrade them so I tied the LS6 mod into the needed replacement of the KS. It works great with a catch can. <<<This can be done with or without doing the LS6 VCT mod.

  7. #7
    Quote Originally Posted by SMWS6TA View Post
    Really?!? I hope you were being sarcastic. That style of PCV has been around for many, many years. It really is not a complete POS, but the mistake that they made was putting it on the rear of the valve covers directly over where the oil is forced up to the valves. They used to have them at the front of the covers but for some reason it was moved to the rear on the LS1.
    I think I was just showing my ignorance - I still have a lot to learn, it seems very bewildering for the beginner that I am.




    Quote Originally Posted by SMWS6TA View Post
    Like I stated in the thread - this is not a performance mod and the LS6 VCT is cheaper part vs the OEM PCV. There is a thread in the tech stickies that gives very good directions. Total time for me to do this took about 2.5 hrs because I had to notch the block while in my driveway. I took my time and didn't rush. I would say that if you are planning on doing something else like replacing the knock sensors or OPSU, things that require you to remove the intake or are doing an intake swap (like going to a FAST 102) I would say wait to do this mod till you do them. Only because you have to do the same work and not have to do it twice. Or if you are like me and loath the OEM PCV setup, just removing the intake is not to difficult. You are lucky because you have a 02' - this means you will not need to notch the block like 98-01's have to make room for the LS6 VCT also you have the LS6 intake (this is a good intake, next better upgrade would be a FAST 90 or 102. 90's are hard to come by because they are no longer made and the 102 has more stuff needed then just the intake and cost $1k.

    I ended up doing this mod because after I did my intake swap I pinched the KS wire harness and had to go back and replace/upgrade them so I tied the LS6 mod into the needed replacement of the KS. It works great with a catch can. <<<This can be done with or without doing the LS6 VCT mod.
    Yes, pajeff02 mentions a catch can in his post as well, that looks to be the most viable option for the time being.

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    Spaz is My Mentor SMWS6TA's Avatar
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    No problem, it's hard to understand if someone is sarcastic on the net....





    My hate for the OEM PCV is because it splits right behind the intake and is one of the main spots that causes vacuum & oil leaks. Most ppl don't know how it is run so they never check back there.

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    Quote Originally Posted by SMWS6TA View Post
    Really?!? I hope you were being sarcastic. That style of PCV has been around for many, many years. It really is not a complete POS, but the mistake that they made was putting it on the rear of the valve covers directly over where the oil is forced up to the valves. They used to have them at the front of the covers but for some reason it was moved to the rear on the LS1.

    oiling is through the pushrods if im not mistaken... those holes are for the oil to drain back down to the pan.

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    Spaz is My Mentor SMWS6TA's Avatar
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    You right my head is not on this week......but the oil is still push into the pcv tube especially with hard launches

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    Quote Originally Posted by SMWS6TA View Post
    No problem, it's hard to understand if someone is sarcastic on the net....





    My hate for the OEM PCV is because it splits right behind the intake and is one of the main spots that causes vacuum & oil leaks. Most ppl don't know how it is run so they never check back there.


    how would you go about checking that area in the back of the intake?

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    Member TA98's Avatar
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    lean across engine, reach hand around back. follow PCV system from valve covers, get scrapes on hands and wonder if what you feel is really what youre going for.

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    Quote Originally Posted by T/A98 View Post
    lean across engine, reach hand around back. follow PCV system from valve covers, get scrapes on hands and wonder if what you feel is really what youre going for.
    not sure how i feel about that, haha! ill use my left hand cause my right hand/arm is tattooed

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    This is what the PCV hose setup looks like. It is rather expensive to buy a replacement from GM. You can replace the hard plastic lines with standard vacuum hoses and I understand that an old spark plug boot can be used for the transition in size at the actual valve. They are known to fail both in the very back corner and at the connection to the throttle body.



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    The other reason for the pcv system is to create negative pressure in the engine which helps to manage oil leaks and of course keeps the fumes and the oil mist out of the engine compartment. The aluminim blocks expand and contract more than cast iron blocks and have more blowby as a result, that was part of the reason that the original PCV system had more oil in it. A catch can inserted in the PCV line works wonders - there is also a TSB to replace the original PCV with the one from the truck engine that has a much smaller orifice.

  16. #16
    Quote Originally Posted by pajeff02 View Post
    This is what the PCV hose setup looks like. It is rather expensive to buy a replacement from GM. You can replace the hard plastic lines with standard vacuum hoses and I understand that an old spark plug boot can be used for the transition in size at the actual valve. They are known to fail both in the very back corner and at the connection to the throttle body.


    Click for full size
    That's a little unsettling, is it the case that it will fail or may fail?

  17. #17
    Spaz is My Mentor SMWS6TA's Avatar
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    All rubber products that come in contact with heat cycles will fail at some point in their life. I took 12 yrs for mine (the pcv) to finally go. I still have the original water hoses. (knock on wood) and my car is a 98.

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    Mine was checking around the PCV valve at 71,500 miles so I elected to replace the whole thing in 2010.

  19. #19
    Just out of curiosity, if you have a catch-can does it have to be connected to the intake or is it feasible to have a second catch-can that could be monitored and emptied back into the engine, via the oil filler, when required?

    Also, does anyone manufacture valve covers that have the PCV connections re-routed to the front?

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    Ive seen catch cans, not on LS1s, that are routed back into the oil pan, but on our cars it would require drilling


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