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2008 CTS Base Manual Tran
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Recently did my timing chains (see my earlier thread for problem I am having still related to that). Anyway, I had watched this video on the 3.6L a while back and sure enough, my engine certainly confirms. There is a distinct difference in discoloration between the right and left sides of the engine. The drivers side on mine looks practically brand new. The passenger side is much darker, likely due to lack of ventilation of the oil vapors. The good news is that the "bad" side of mine looks similar to the good side in the video! I did try for a few months the trick of drilling out the ventilation barb to improve air flow, but at least for me, that caused other issues (periodic misfires and puff of smoke upon startup). I ended up going back to an OEM barb.

Anyway, I think with mine it shows that even the bad side is still not terrible after 135k miles, so if you use quality oils and keep up with changes, the engine will not have major problems due to this issue. Ironically the bank I am now having issues with is that beautiful looking drivers side!

https://share.icloud.com/photos/0FTuM0XaC6Gl0dYUgwYYvSy9w


Also, here were the old vs new chain length comparisons. All 3 original chains were consistently about 3/4" longer than the new chains.

 

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08 CTS DI
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I warned against the PCV modification after trying it myself immediately following an oil change and coming up about a 1/2 quart low after the 80 mile drive that followed. Seems if you allow more air through that passage without increased baffling, you will also allow more oil mist as well. Likewise, I fixed it with a new unmodified PCV.

Unfortunately the tinting on the passenger side cylinder head is a result of reduced fresh airflow over it compared to the driver side due to the design. I noticed it when I changed my timing components also. The good news is that if you use a quality motor oil and change it on schedule your motor will never look like the one in the video you linked to, except maybe at 300k miles.

My timing chain thread is on here somewhere, but I doubt I'll ever get cozy enough with the new forum layout to find it. I had similar elongation in the timing chains, why on earth I didn't take a picture I don't know. I do still have all of the old components.

The puff of smoke you experienced on startup with the PCV modification was probably from the additional oil that was entering the intake, after it had time to settle and pool up a little before the next startup.

Note your oil consumption rate after the chains are sorted out. I read in a recent posting somewhere that one of the signs of elongated chains short of tripping the engine light is increased oil consumption although I didn't experience that.
 

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'09 CTS DI FE1 Luxury
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I drilled my PCV restrictor as detailed all over the www and haven't had any problems. I'm sure it helps that I installed a catch can at the same time. I used a 5/64" bit for the bottom holes and 7/64" for the top hole. IIRC each hole was enlarged by about 1/64" (not much).
 

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From the little I recall regarding the modification, it was to address clogging of the valve, but since it is a serviceable part, routine replacement would prevent that. To the OP, Changing the passage diameter wouldn't correct the partition area (seen in the video link) on the head, that blocks airflow over it so the discoloration wouldn't be prevented.

The increased airflow resulting from the modification will change the normal throttle position at idle by requiring it to close more in an effort to achieve the commanded idle rpm. I recall having a code set once temporarily after the modification, addressing that needed correction, which should have been my reason for returning it to normal, instead of the oil consumption that followed. It sounded like a good idea without thinking it through. Glad I checked the oil level in time.

I remember PCV clogging being more of an issue on the first gen for some reason but, am not sure. The newer valve cover gasket (Fel-Pro, Mahle) for that side contains a baffle in the space beneath the PCV with small holes in it, in an effort to help abate the amount of oil mist passing through it since the cover has no baffle on that side.

There are still gaskets available that do not have that improvement, which I suspect all of the Gen ones had. The oil catch can alone is likely the best upgrade to reduce oil flow into the intake.
 

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I believe the primary reason for enlarging the PCV orifices is to improve scavenging of blowby gasses and moisture from the crankcase. GM did the same thing on 2013+ engines. Any slight effect on the idle air circuit is insignificant. When I first started my engine immediately after performing this mod the idle speed was unchanged. Now if the holes were opened up too much, that could cause issues.
 

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I believe the primary reason for enlarging the PCV orifices is to improve scavenging of blowby gasses and moisture from the crankcase. GM did the same thing on 2013+ engines. Any slight effect on the idle air circuit is insignificant. When I first started my engine immediately after performing this mod the idle speed was unchanged. Now if the holes were opened up too much, that could cause issues.
I would hope that when GM made this change, there were some other changes to accompany it, given it was done on the 2013 which is the LFX motor. I say that because the same change made on the LLT and LY7, with all else the same is counter productive, in that reducing the air flow restriction at the PCV, will allow more air and oil mist into the intake behind the throttle body and it still does nothing for the partitioned off area of the right cylinder head.

It will also have little effect on the free flowing driver side, when engine rpm climbs (throttle opens) and crank case combustion gasses increase and over run the smallish PCV orifice and move in reverse direction, taking the path of least resistance into the air tube, where many have complained of sizable oil puddling already.

That's where the oil that fouls up the throttle body comes from. When the PCV clogs up, the gasses flow continuously and in greater quantity through the left valve cover back into the engine is what I recall as the reason for the modification.

With an oil catch can inline at the PCV point, the residue would be greatly decreased, but the possibility of pooling oil in the catch can instead of the intake still remains. My objective would be to keep as much of the oil as possible in the crankcase.

Someone posted here a short while back about dumping a large quantity of oil out of the intake tube reservoir which some tubes have so it varies from car to car. The air intake tube on my Mom's LY7 keeps a "healthy" quantity of oil in it so there's no way I'd modify the PCV to give it a more direct route to the intake.

Whatever the case, modify with caution.
 

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Great points. If the only concern is to limit oil ingestion and intake valve deposits you are 100% correct. However, if the oem pcv orifice size is too small to allow adequate blowby gas and moisture evacuation from the crankcase, the resulting motor oil contamination could be even more detrimental than more frequent catch can emptying and oil level checks. Whether the oem PCV orifice sizes are adequately sized or not is debatable and I have no direct evidence to support either position. There are others who feel very strongly that the oem orifices are too small and that GM recognized this in 2013.

I wouldn't recommend drilling the PCV barb without installing a catch can. I also can't state definitively that the oem pcv holes are too small for adequate blowby gas scavenging. All I can say is that so far it's working fine for me. I will post back if I discover any unwanted side effects from the mod. Your concerns with this mod are quite valid.
 

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2011 CTS Performance Coupe -3.6 DI 6 Speed Manual
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The intent of opening up the holes is to reduce the velocity at the orifice. You have the same amount of air being scavenged just at a slower rate thereby allowing some of the droplets of oil to fall out prior to entering the system and only allowing vapor to go into the intake or catch can.
 

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Great points. If the only concern is to limit oil ingestion and intake valve deposits you are 100% correct. However, if the oem pcv orifice size is too small to allow adequate blowby gas and moisture evacuation from the crankcase, the resulting motor oil contamination could be even more detrimental than more frequent catch can emptying and oil level checks. Whether the oem PCV orifice sizes are adequately sized or not is debatable and I have no direct evidence to support either position. There are others who feel very strongly that the oem orifices are too small and that GM recognized this in 2013.

I wouldn't recommend drilling the PCV barb without installing a catch can. I also can't state definitively that the oem pcv holes are too small for adequate blowby gas scavenging. All I can say is that so far it's working fine for me. I will post back if I discover any unwanted side effects from the mod. Your concerns with this mod are quite valid.
GM along with many if not all other auto manufacturers have been using PCV valves for far too long to not know if the PCV in place is sufficient for the application and THEIR PURPOSE. Some things are the way they are by design whether we the consumer appreciate it, or would prefer to have it changed. The PCV is a serviceable part that should be replaced as routine maintenance so that it never gets clogged in the first place.

We may not like it, but oil mist into the intake along with combustion gases is part of the emissions limiting process.The increased diameter of the 2013 PCV could have as much to do with the compression bump, the increased intake camshaft duration, the different throttle body, and the higher power output relative to the LLT all of which could and probably does require more crank case venting, while at the same time having nothing at all to do with the assumptions some have made about the previous PCV. There's too much different between the motors to assume GM ignored all of it and made the change solely because of what others here have decided is a good idea.

I'm just using mind reasoning here. Oil is entering the intake from both valve covers. That alone defeats the PCV modification, once that fact is acknowledged. If you add the oil catch can, there's no need for the PCV modification. I enjoy the subject of engine related performance, but modifications have to make sense for me beyond just theorizing.
 

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The intent of opening up the holes is to reduce the velocity at the orifice. You have the same amount of air being scavenged just at a slower rate thereby allowing some of the droplets of oil to fall out prior to entering the system and only allowing vapor to go into the intake or catch can.
If you open up the holes in the PCV, you allow more air into the intake through the PCV, not the same amount, because the engine rpm will increase above the commanded idle rpm. The PCM will close the throttle blade more to counter act that effect, which will apply more vacuum to the airflow through the PCV, not to mention no one knows how slow the flow has to be for the theory to be effective.

In order for the flow through the PCV to be slowed, the throttle blade has to stay put, allowing the engine rpm at idle to increase above commanded. In other words, in order for this to possibly work as planned, the PCM has to be reprogrammed. The motor is moving the same amount of air at idle, except more of it is coming through the PCV. The particulate in the blow-by gas is independent of the flow rate through the PCV, it's a mist more so than droplets. I don't expect a greater volume of airflow through the PCV, to deliver less oil mist into the intake.

If you're emptying oil from the oil catch can after this modification, that's proof.
 

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'09 CTS DI FE1 Luxury
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GM along with many if not all other auto manufacturers have been using PCV valves for far too long to not know if the PCV in place is sufficient for the application and THEIR PURPOSE. Some things are the way they are by design whether we the consumer appreciate it, or would prefer to have it changed. The PCV is a serviceable part that should be replaced as routine maintenance so that it never gets clogged in the first place.

We may not like it, but oil mist into the intake along with combustion gases is part of the emissions limiting process.The increased diameter of the 2013 PCV could have as much to do with the compression bump, the increased intake camshaft duration, the different throttle body, and the higher power output relative to the LLT all of which could and probably does require more crank case venting, while at the same time having nothing at all to do with the assumptions some have made about the previous PCV. There's too much different between the motors to assume GM ignored all of it and made the change solely because of what others here have decided is a good idea.

I'm just using mind reasoning here. Oil is entering the intake from both valve covers. That alone defeats the PCV modification, once that fact is acknowledged. If you add the oil catch can, there's no need for the PCV modification. I enjoy the subject of engine related performance, but modifications have to make sense for me beyond just theorizing.
Yes, auto manufacturer's have also been using timing chains and sunroof drains for far too long to not know if the timing chain and drains in place are sufficient for the application and THEIR PURPOSE. Witness the '08-09 GM LLT V6 timing chain and G2 CTS sunroof drains, etc., etc. Auto makers make a lot of mistakes and often correct them in subsequent model years. Sometimes the aftermarket or owners fix these deficiencies.

IIRC you stated previously that you drilled your PCV restrictor holes larger than the recommended 5/64" and 7/64". Do you remember how much larger you went? Could that not have contributed to your poor experience with and opinion of this mod?
 

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The timing chains and sunroof drains may not necessarily have been as much of a mistake as we assume, especially the timing chains. Some of these gotchas! are by design to feed the "profit machine" through planned obsolescence/failure. The cost of the timing chain job is an excellent "Get a new car, or fix it?" cross road that is probably here to stay. How about those module programming costs outside of warranty that will insure each and everyone of us remains subject to manufacturer kickbacks every time one fails, for the life of the car.

I may have made all of the holes the same size. The effect is the same, although with not as much flow increase when corrected to theory specs, because the volume of flow through the valve is still increased. As a matter of fact, in accordance with the theory, the flow velocity through my valve should have been even slower allowing even more oil to theoretically drop out of suspension and I know that did not happen.

It's important to note that we're dealing with mostly vacuum pressure on the valve, not a scavenging effect and at some point higher in the rpm range that vacuum may be substituted by pressure in the crankcase for brief periods.

Think about it, when the hole is enlarged above stock diameter, the velocity of gasses through it is reduced on a small scale, but the volume increased, that's why the throttle has to be closed down some to counter the effect on idle rpm. Still, the velocity through that valve is very high because 3.6 liters of motor, minus what comes through the throttle are pulling on it. The port on the driver side cover is considerably larger and it also contributes to the oiling of the intake so the theory doesn't pan out.

I believe a much longer hose by a few feet and coiled would actually have more of the desired effect of separating the oil out of suspension before reaching the intake.
 
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