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Clearing up misconceptions of PCV systems

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Old 08-27-2008, 06:40 AM
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Originally Posted by sswoody00
I'd also like to know this, as I'm about to do the LS6 valley cover swap. Is the LS6 PCV designed to flow better with the rear ports blocked, or would it be better to leave the stock LS1 PCV intact to supplement the new valley?
We usually block the rear valve cover fittings if a breather in the oil cap is used when converting to the LS6 valley cover, but if not use the drivers side rear as an inlet as well as the pass frnt. Just "tee" in a line so it connects with the fresh air line to the TB. Then you get fresh air entering both valve covers, travels down both pushrod valley's, and through the crankcase & out the valley cover for a more complete "flush".
Old 08-27-2008, 07:09 AM
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I have a catch can, I forget who's, but it looks and sounds very similar to yours. My issue is that I inadvertantly ditched my PCV valve, so I need to replace it. What's the best reccomendation, should I stick with the stock one or should I get a different one?

Thanks.
Old 08-27-2008, 12:20 PM
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Originally Posted by The Alchemist
I have a catch can, I forget who's, but it looks and sounds very similar to yours. My issue is that I inadvertantly ditched my PCV valve, so I need to replace it. What's the best reccomendation, should I stick with the stock one or should I get a different one?

Thanks.

Get a stock replacement....it will work just fine. W/out one you will draw to much vac through the can & it will draw oil right through most.
Old 08-27-2008, 07:53 PM
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TLewis4095,

Great information; Thank-you!


Moderators, This information really needs to be a sticky.
Old 08-27-2008, 08:24 PM
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Originally Posted by TLewis4095
We usually block the rear valve cover fittings if a breather in the oil cap is used when converting to the LS6 valley cover, but if not use the drivers side rear as an inlet as well as the pass frnt. Just "tee" in a line so it connects with the fresh air line to the TB. Then you get fresh air entering both valve covers, travels down both pushrod valley's, and through the crankcase & out the valley cover for a more complete "flush".

Okay I have a 383 (LS6 block) built by a highly respected shop (before the owner passed away) obviously using the LS6 valley. My driver side rear port is capped as well as the passenger rear. The only tubes I have are from the passenger front outlet to my TB and from the LS6 valley to my intake. Are you saying this motor is not being vented properly??
Old 08-28-2008, 05:18 PM
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Originally Posted by sswoody00
SS1875 - As far as I can tell from reading up on the PCV systems, yours sounds like it's hooked up correctly You have your PCV valve inline between your valley and manifold, correct? Then it should all be good
Actually no I don't. Guess I better get in huh.
Old 08-28-2008, 05:21 PM
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Originally Posted by sswoody00
TLewis - Thank you very much for all your VERY helpful posts. I've researched a lot into the PCV issues, and you seem to know your stuff very well, and are very helpful with your advice. So just to pick your brain, and to make sure I have everything right, if I swap to the LS6 valley, and put a breather filter on the oil filler cap (very large cammed car with full bolt-ons) I can pretty much block off everything besides the tube from the valley to the manifold, correct? And also with your catch can, do I still need to run a PCV valve before the manifold, or is the one in the catch can good enough on its own?
The one in the catch can will do. You have it down pretty good...make sure to post your results.
Old 08-28-2008, 09:14 PM
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THanks for the reply and the help.
Old 08-29-2008, 12:30 AM
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Originally Posted by TLewis4095
a known tuner
A very well known tuner (who should know better).
Old 08-29-2008, 12:03 PM
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For those w/ an LS6 valley cover/PCV set-up & a grommet style valve cover on the rear of the driver's side head, this may be of interest. After reading this thread, I added a miniature cone filter, mounted in the grommet to get filtered air into the head. Was gonna go w/ a standard breather, but, it wouldn't clear the fuel rail cover. The mini cone filter does & the install looks clean. Just use an old PCV valve (modified) as an adapter. Cone filter mounts on the PCV valve nipple & the other end of the PCV valve is pushed into the grommet. In order to use the old PCV valve, you must first remove the plunger. Just gently grind the bottom plate off (where the plunger seats) to release the plunger & spring. Then clean up the burrs & it's done.
Old 08-29-2008, 12:41 PM
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Originally Posted by LS1-450
For those w/ an LS6 valley cover/PCV set-up & a grommet style valve cover on the rear of the driver's side head, this may be of interest. After reading this thread, I added a miniature cone filter, mounted in the grommet to get filtered air into the head. Was gonna go w/ a standard breather, but, it wouldn't clear the fuel rail cover. The mini cone filter does & the install looks clean. Just use an old PCV valve (modified) as an adapter. Cone filter mounts on the PCV valve nipple & the other end of the PCV valve is pushed into the grommet. In order to use the old PCV valve, you must first remove the plunger. Just gently grind the bottom plate off (where the plunger seats) to release the plunger & spring. Then clean up the burrs & it's done.
Excellent addition to this thread. The gromet fits great & it allows for a good fresh air path through the crankcase.
Old 08-29-2008, 12:46 PM
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This is great info, thanks!
Old 08-29-2008, 01:03 PM
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Originally Posted by TLewis4095
Excellent addition to this thread. The gromet fits great & it allows for a good fresh air path through the crankcase.
The fresh air that enters the passenger side valve cover has passed through the MAF and is therefore "measured".

Wouldn't adding a filter onto the drivers side valve cover be allowing unmetered/un-measured air into the crankcase ? The volume of this air (though small) does get consumed by the engine, but the computer won't know about it.
Old 08-29-2008, 01:05 PM
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2 questions...

1. With the integrated PCV in your catchcan... what happens when it's time to replace the PCV as I'm sure it doesn't last forever....?

2. I'm a little confused as to what's keeping the oil from shooting out the valve cover breather if I were to get one like pictured below... I've heard of people putting these on their valve covers, and oil coming out through the filter and next thing ya know, it's all over the engine bay...



thanks
Old 08-29-2008, 02:00 PM
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Originally Posted by HSV-GTS-300
The fresh air that enters the passenger side valve cover has passed through the MAF and is therefore "measured".

Wouldn't adding a filter onto the drivers side valve cover be allowing unmetered/un-measured air into the crankcase ? The volume of this air (though small) does get consumed by the engine, but the computer won't know about it.

I thought about this prior to adding the filter & decided that since oil cap breathers are known to work (not MAF measured air) then this should work as well. Have noticed no idle issues.

EDIT: I will also log STFT's next chance I get. IF the PCM is effected by the non-measured air, then the STFT's will show it.

Last edited by LS1-450; 08-29-2008 at 02:15 PM.
Old 08-29-2008, 04:51 PM
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Originally Posted by Soul TKR
2 questions...

1. With the integrated PCV in your catchcan... what happens when it's time to replace the PCV as I'm sure it doesn't last forever....?

2. I'm a little confused as to what's keeping the oil from shooting out the valve cover breather if I were to get one like pictured below... I've heard of people putting these on their valve covers, and oil coming out through the filter and next thing ya know, it's all over the engine bay...



thanks

Only if the system is not setup properly or if you have excessive blowby will oil spew out a breather in the valve cover/oil cap.

As for the PCV valve it is easy to replace and can be done by the user if needed. Seeing as a dealer will charge over $100 to change most PCV valves, at $69.99 you can buy a new catch can cheaper if you don't want to replace the valve if needed.
Old 08-30-2008, 01:23 PM
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Originally Posted by LS1-450
I thought about this prior to adding the filter & decided that since oil cap breathers are known to work (not MAF measured air) then this should work as well. Have noticed no idle issues.

EDIT: I will also log STFT's next chance I get. IF the PCM is effected by the non-measured air, then the STFT's will show it.



UPDATE:

STFT's are maxed w/ the head vented to un-measured air. This indicates that the PCM is adding fuel for a lean condition. Once sealed (all measured air used), the STFT's returned to normal. So, I ran a hose from the second passenger side head port to the inlet that was installed on the driver's side head. This means that now, only measured air is used as a fresh air feed to the valve covers & all is well.

NOTE: For those whom have had both valve covers previously sealed (no fresh air) your oil pressure will drop when you add metered air to the valve covers. A stock oil pressure gauge won't even show it & it's not an issue.


EDIT: Oh Damn, I forgot. The vacuum pressure is higher w/ the measured, added air source to the valve covers.
(this is the likely reason for the oil pressure drop). The increased measured air was 1.7 to 2% & I adjusted my MAF table accordingly. So, there is now 2% more air entering the engine as a result of feeding air to the valve covers. This does not mean that anyone needs to modify their MAF table as a result adding valve cover air because your PCM will adjust for it & 2% is nothing in terms of affecting a tune. I noted it to show the measured benefit that TLewis4095 has drawn our attention to. So, his method (using measured air) results in better vaccum (-pressure) & the flushing out aspect of it.

Thanks again TLewis

Last edited by LS1-450; 08-30-2008 at 01:37 PM.
Old 08-30-2008, 08:45 PM
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Slight tangent:

I have a carb'ed LS-1 with smoothed (welded and ground) valley cover and Aaron's smoothie welded valve covers. Obviously no PCV at this time. The carb has a port for PCV, would I drill the valley cover and install at that location? Would a stock PCV work OK?

Thanks!

Russ
Old 08-30-2008, 09:45 PM
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I can vouche for the revxtreme catch can works well, easy to install and looks great well worth the money! thanks again guys!
Old 08-31-2008, 09:16 AM
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Originally Posted by S10xGN
Slight tangent:

I have a carb'ed LS-1 with smoothed (welded and ground) valley cover and Aaron's smoothie welded valve covers. Obviously no PCV at this time. The carb has a port for PCV, would I drill the valley cover and install at that location? Would a stock PCV work OK?

Thanks!

Russ
You would need to add a fresh air source (breather in the oil fill cap probably the easiest) and then to pull the vapors out if the vally cover is not baffled you may need to add a fitting to the drives side rear. Run a oil seperating can inline between the carb vac fitting & the valve cover fitting.

Originally Posted by Bouvs
I can vouche for the revxtreme catch can works well, easy to install and looks great well worth the money! thanks again guys!


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