PCV on engine valley cover

[TheBrightSide]

​​⁠So, I noticed that with the late LS1 and LS6 engines, they started revising the PCV ports to route to the outside of the engine valley cover. I guess on these setups, they had it directly fed vacuum from the intake manifold (usually right above it, right before the throttle body), to pick up from the PCV port from outside of the valley cover.

I wonder what the PCV setup is like, for the engines that have a non-AFM/DOD setup, but also don’t have an external PCV valve/port on the outside of their valley cover? I know the identical engine to my LS3 would be the L99 (comes factory with DOD/AFM), and that engine doesn’t have the external PCV port on it’s valley cover. However, even after deleting DOD/AFM, it looks like people still skip the option for the external PCV port sometimes. Does anyone know how this works?

I’m asking this primarily because I’m about to replace the engine valley cover on my LS3, as a means of process of elimination, for some serious oil consumption through the PCV valve/port on my valley cover. I don’t think it could help unless the baffle system somehow had an issue. However, the baffle system (made from ABS plastic?) is glued down onto the valley cover, even though there’s removable bolts. Looks like you have to buy the valley cover as a whole, if your PCV system (the “baffling”) goes bad…

[1JEWLDSSRS]

Originally Posted by TheBrightSide

​​⁠So, I noticed that with the late LS1 and LS6 engines, they started revising the PCV ports to route to the outside of the engine valley cover. I guess on these setups, they had it directly fed vacuum from the intake manifold (usually right above it, right before the throttle body), to pick up from the PCV port from outside of the valley cover.

I wonder what the PCV setup is like, for the engines that have a non-AFM/DOD setup, but also don’t have an external PCV valve/port on the outside of their valley cover? I know the identical engine to my LS3 would be the L99 (comes factory with DOD/AFM), and that engine doesn’t have the external PCV port on it’s valley cover. However, even after deleting DOD/AFM, it looks like people still skip the option for the external PCV port sometimes. Does anyone know how this works?

I’m asking this primarily because I’m about to replace the engine valley cover on my LS3, as a means of process of elimination, for some serious oil consumption through the PCV valve/port on my valley cover. I don’t think it could help unless the baffle system somehow had an issue. However, the baffle system (made from ABS plastic?) is glued down onto the valley cover, even though there’s removable bolts. Looks like you have to buy the valley cover as a whole, if your PCV system (the “baffling”) goes bad…

What we did on my L99 when we did the cam swap and LS3 conversion and installed the LOD manifold, we deleted the original PCV system, installed an LS3 valley tray, hooked up the port on the tray to the intake port on my catch can, out port on the catch can went to the back of my manifold, passenger side valve cover port went to a fitting on my CAI tube between the MAF and TB, driver side valve cover was capped off. The PCV purge selinoid tube is just vented to atmosphere, and tuned out. The original PCV tube went from a fitting on the stock manifold just behind the TB on the driver side, the tube went around the front of the manifold around the passenger side to the selinoid. Since I had the L99 with the AFM/DOD, the stock valley tray did not have a vacuum port like the LS3,

[TheBrightSide]

Originally Posted by 1JEWLDSSRS

What we did on my L99 when we did the cam swap and LS3 conversion and installed the LOD manifold, we deleted the original PCV system, installed an LS3 valley tray, hooked up the port on the tray to the intake port on my catch can, out port on the catch can went to the back of my manifold, passenger side valve cover port went to a fitting on my CAI tube between the MAF and TB, driver side valve cover was capped off. The PCV purge selinoid tube is just vented to atmosphere, and tuned out. The original PCV tube went from a fitting on the stock manifold just behind the TB on the driver side, the tube went around the front of the manifold around the passenger side to the selinoid. Since I had the L99 with the AFM/DOD, the stock valley tray did not have a vacuum port like the LS3,

Gotcha. I don’t think I might have to do that, and I’m not sure if that’s a specific setup to maybe run for forced induction/boost. Was there any specific reason you ran this, besides having an aftermarket intake manifold?

I’m mainly sticking to the factory intake manifold, and I’m also trying to keep it emissions compliant (gonna retain the same placement for the purge solenoid hard plastic line, to the intake manifold inlet on driver side behind TB). I’m mainly trying to figure out how the PCV system works, for both the factory LS3 engine valley cover, and also for the aftermarket valley covers that don’t have the external port on the valley cover (also doesn’t have a PCV system underneath it).

I’m experiencing lots of oil going through the PCV on my stock valley cover, so I was about to replace it, for a means of process of elimination. Not sure if that’s gonna help, but that’s why I was asking if anyone knew specifically how the PCV system worked on the LS3 valley covers. It looks like there’s a few openings on the baffle “system” under the cover, and then there’s some perforations/holes towards one side.

The baffle system on the valley covers with the external pcv port, are bolted down to the cover, but it also looks to be sealed or glued on, and thus can’t be removed without potentially prying it off and breaking the plastic/composite material baffle system. I figured going back to your alternative routing, I was debating capping off the pcv port to the LS3 valley cover, and running a hose all the way from the originally capped off driver side valve cover PCV/breather(?) port, back to the intake manifold inlet (to the passenger side of stock intake manifold, right behind throttle body).

I have an OCD habit of topping off my oil, even when it doesn’t have to necessarily be done. But this time around, I’ll let the engine do it’s thing until it’s time for an oil change. I dump out my near full oil catch can every 3-4 weeks, with daily driving, so I have a good feeling at least maybe at least 3/4 to a full quart of oil (or even more), may be consumed by the time I go to check my engine oil level before doing my oil change.

[1JEWLDSSRS]

I didn't pay any attention to what was under my original valley tray as far as baffles go, just know that there was a bunch of AFM crap on it. I replaced it with an LS3 valley tray I got from Summit Racing, and I don't recall anything being on the bottom of it. Here's some info for you to look through. And to your question as to why I ran that setup, it was due to the manifold I have. The car is NOT boosted, just NA'd..

https://www.bing.com/images/search?q...m=IGRE&first=1

This is the valley tray I used..

https://www.summitracing.com/parts/nal-12599296

[J35Y2]

Originally Posted by 1JEWLDSSRS

I didn't pay any attention to what was under my original valley tray as far as baffles go, just know that there was a bunch of AFM crap on it. I replaced it with an LS3 valley tray I got from Summit Racing, and I don't recall anything being on the bottom of it. Here's some info for you to look through. And to your question as to why I ran that setup, it was due to the manifold I have. The car is NOT boosted, just NA'd..

https://www.bing.com/images/search?q...m=IGRE&first=1

This is the valley tray I used..

https://www.summitracing.com/parts/nal-12599296

Yep, if you look up the parts number, that's the LS3 engine valley cover, which has the PCV system underneath it, and the external port at the corner of the top. There's the LS2 engine valley cover (P/N 12570471), which is more or less almost exactly identical, except the external PCV port has the hose barb towards the end of port, rather than in the middle of the port (LS3 valley cover).

[J35Y2]

Here's the bottom of the LS2/LS3 (LS Gen IV) engine valley cover. On the sides of the black plastic PCV baffle thing, there's two open slots, but I'd have to take close-up photos, to maybe show you and have others maybe see what's going on with it. If you see the perforated holes on the other end, I have no idea what those do; but I assume some oil may be picked up through it?

[TheBrightSide]

I ended up replacing my bone stock engine valley cover on my LS3, for a new one that I got from Texas Speed Performance. It seemed pretty much identical, and came with a brand new cover gasket, and the small round gaskets that go under the valley cover. I didn’t see anything weird or out of place, and I don’t know 100% how the PCV system under the valley cover works, but I’m hoping it might help the oil “blow-by” to either a much, much lower amount, or stop it almost altogether.

When I was messing with the intake manifold port, that is supposed to be connected to the PCV port coming out of the valley cover, I ended up breaking the nipple/port completely clean off.. I ended up putting in a straw on the inside, and used it to “bridge” the broken section of the port, to the rest of it’s structured port going to the inside of the manifold. This should’ve cut down the air flow/vacuum by a lot, but it doesn’t look like it did at all.

There’s a very light film of engine oil towards the back of the stock intake manifold (ported, with rod mod), and I usually clean out oil and debris when I usually take the intake tube and throttle body off. When I smog/emissions test bi-annually in my state, I plan to connect the little hose that connects the valley cover PCV port, to the intake manifold port, right on the side, behind the throttle body. Depending on whether there’s still engine oil being tossed up into the intake manifold, I usually just leave my oil catch can lines disconnected off to the side, and then reinstall after getting it smogged. I usually just run an intake valve/upper engine cleaning solution, through the intake tube or an intake manifold port, up close to the throttle body.

[InFiD3ViL]

The LS3 valley cover simply has a vacuum port, not housing any of the actual PCV system components, but does of course connect to the overall PCV 'system'. The L99 didn't have this vacuum port due to the VLOM system being integrated into the valley cover for the AFM oil towers, and also did not house the PCV. Hence when installing a catch can, the routing is different between LS3/L99 applications.

The VALVE covers are where the PCV system is integrated on our engines, not the valley covers. There are some differences between different versions of the LS engine, such as the LS6, that did have part of the PCV system in the valley cover. There is a metered orifice in the LS valve cover instead of a traditional PCV valve like on older generation engines. Regardless, neither the LS3, nor the L99 has the PCV in the valley cover.

The Gen III LS engines had a known issue with the PCV baffles in some of the valve covers, causing excessive oil consumption. The Gen IV valve covers were updated to fix this issue. If you have oil consumption issues I would start at the valve covers and also check for proper vacuum line routing. Whether Gen III or Gen IV, the orifice in the valve cover baffles can become clogged, causing issues - especially prone on engines with poor maintenance.

[TheBrightSide]

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[TheBrightSide]

Originally Posted by InFiD3ViL

The LS3 valley cover simply has a vacuum port, not housing any of the actual PCV system components, but does of course connect to the overall PCV 'system'. The L99 didn't have this vacuum port due to the VLOM system being integrated into the valley cover for the AFM oil towers, and also did not house the PCV. Hence when installing a catch can, the routing is different between LS3/L99 applications.

The VALVE covers are where the PCV system is integrated on our engines, not the valley covers. There are some differences between different versions of the LS engine, such as the LS6, that did have part of the PCV system in the valley cover. There is a metered orifice in the LS valve cover instead of a traditional PCV valve like on older generation engines. Regardless, neither the LS3, nor the L99 has the PCV in the valley cover.

The Gen III LS engines had a known issue with the PCV baffles in some of the valve covers, causing excessive oil consumption. The Gen IV valve covers were updated to fix this issue. If you have oil consumption issues I would start at the valve covers and also check for proper vacuum line routing. Whether Gen III or Gen IV, the orifice in the valve cover baffles can become clogged, causing issues - especially prone on engines with poor maintenance.

I did a compression test recently, and everything seemed okay/within range. I replaced the engine valley cover with a new one. I have an early production 2009 LS3, so my driver side valve cover is the older one; but the PCV port is blocked off and unused anyways…

The passenger side engine valve cover, though, I didn’t see anything crazy with it, nor did I notice oil issues. It simply connects to my intake hose/breather valve, for metered air. If I leave it wide open, it will usually throw a lean CEL code.

Other than that, I don’t notice anything blowing out of my engine oil filler port (through the passenger engine valve cover). I run an Elite Engineering oil catch can, with 2 added check valves on each of my two inlet/outlet hose routings. I have to dump it out every 2-3 weeks, based on the amount of daily driving that I do with my car. I haven’t yet checked with the new valley cover installed, but will update soon within the next month or so.