Question : 3500 (LX9) PCV System

[jmgtp]

I'm in the final stages of getting my LX9 swap done, I've even started and ran the engine at this point.
I don't understand something about the LX9 PCV system - the lack of the PCV Valve.

There is a vacuum line that runs from the front rocker cover to the plenum - this line sees full manifold vacuum at all times. There is a second line that runs from the rear rear rocker cover to the intake tube (no vacuum, just filtered air). So, I understand the flow of the system, vacuum on the front cover and atmospheric pressure on the other. What I don't understand is that I don't see a VALVE anywhere? Most other PCV systems I have seen include a valve that limits vacuum a bit and only allows for flow in one direction. The LX9 as I see it does not implement such a valve. Is it not necessary? Is the valve cover internally baffled in such a way so as to not ingest oil through the vacuum side? I've seen something like that on a Quad4 (or whatever the later iteration of that motor was called) where it had some kind of plastic oil separate box in luei of a PCV valve. The last v6 pushrod motor I owned was a 3.1 Beretta and that had a PCV valve.

Can someone confirm that this motor does not use the valve, or has it built in to the rocker cover, or implements a baffle to separate oil from the air flow? The motor is bone stock pulled from a Malibu so I'm sure it is correct as is but if anything I just want a better understanding of how the PCV system on this engine works.

[bszopi]

Got a pic of the front valve cover? Last I remember, the PCV valve is in the front valve cover, and there is a piece of metal that goes over it and is riveted to the valve cover, basically making is a maintenance free part.

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[Jonpro03]

Got a pic of the front valve cover? Last I remember, the PCV valve is in the front valve cover, and there is a piece of metal that goes over it and is riveted to the valve cover, basically making is a maintenance free part.

X2 mine was riveted on to the valve cover.

[jmgtp]

I'll take a pic tonight. There is not anything riveted to the front cover. There is a nipple pressed into it to which the vacuum hose connects. It may be the case that the 'valve' turns out to be the pressed in nipple. I suppose I can try to blow air into it and if I cannot that means there is a valve. The rear cover has a rubber grommit that the fresh air hose fits into.

[CNCguy]

To date, I have not seen that setup on an LX9 but I do know the LZ engines are configured that way. What year is the engine?

[Mars]

Yeah, for some reason on my 3500 (2006) the PCV valve is kind of cast into the valve cover and it is Not actually a check valve. If you were to boost one of them you'd be boosting the crank case. I went to an older 3400 valve cover with the removable PCV valve...

Either that OR maybe my 3500 one was defective...

[jmgtp]

The LX9 is from a 2005 Malibu (and it does have the 7484 crankshaft).

I forgot to take a pic!

It sounds like I have the same setup that Mars motor came with.
I did look at it closely last night and there is nothing riveted to the cover, just a nipple pressed into it for a hose to connect to. I think inside the cover there is likely just a baffle to prevent oil ingestion and no valve so the manifold is likely drawing full vacuum on it all the time.

[pocket-rocket]

Full vacuum is good anyways

[Mars]

I just tested a couple stock 3X00 PCV valves and they don't hold boost for shit. Like major leak. I'm going to retrofit some Supra PCV valves... Should likely upgrade my Cavalier too...

[jmgtp]

Revisiting this thread now that my motor is up and running.

I noticed something on my LX9 that seems abnormal and that is a small amount of oil in the mouth of the throttlebody. There are only 2 places that could introduce oil to this area. The PCV vacuum line and the PCV fresh air line (I am using a 3.4 dohc throttlebody that has a non vacuum port to connect the 'intake' side of the PCV that runs to the rear rocker cover).

Earlier in this thread it was determined that the LX9 is not using any kind of 'valve' to limit vacuum to the front rocker cover, I made the assumption that the front rocker cover has an internal baffle to separate oil from air. Could it be the case that it is still ingesting oil through the vacuum line? I notice a good deal of dark smoke out the pipes when I rev it. It is running rich (I am just now working on the tune) and I assumed it to be fuel but it is a bit greyyish in color so perhaps it can be oil as well.

Has anyone noticed a similar issue with their LX9? I am going to double check to make sure that the line to the rear rocker cover is in fact connected to a NON vacuum port. If it is connected to vacuum that very well could be my problem. But if not, and I suspect not, I believe I am ingesting oil into the intake under vacuum. I may install a pcv valve inline to see if the restriction reduces oil ingestion.

The total oil I noticed in the TB was maybe a 1/4 teaspoon. My other thoughts on the greyyish smoke (if oil) is that my motor has been sitting for years - an unknown amount of time in the junkyard and about 1 year on my engine stand - is it possible that the rings are stuck and it needs some good hard acceleration to reseat them?

Thoughts? Similar issues? Resolutions?

edit: forgot to say, that I noticed the oil the day after I ran it. It is not as if I run it, shut it down, and then there is instantly oil in the TB mouth.

[jmgtp]

Just to finish off the thread, in case someone comes across it in a search some day it will have complete info...

The PCV was sucking oil. I disconnected it and after some running the motor cleared out what oil was left in the manifolds and ran clean. I installed a catch can inline on PCV vacuum line and the system seems to be working well.

One thing I don't fully understand is that I am using the stock LX9 PCV system, which I imagine was engineered not to ingest oil, but it did and the catch can allows separation of oil from air so the oil picked up doesn't make it into the intake manifold.

[jmgtp]

Update... I'm still stucking some oil right through the catch can. Ok its not a "catch can" really, its an air compressor water separator, works in the same manner though probably not quite as good as the real deal. If you google it many have used air compressor water separators with good results. One thing they do mention is that over time it can clog up.

I think the only solution is to install a PCV valve inline, this thing shouldn't need a catch can at all. I don't know why the LX9 doesn't have one but I think restricting some of the vacuum is going to cure it.

[young gun]

Hey sorry for such an old bump but it pertains to the issue at hand..

I just tested a couple stock 3X00 PCV valves and they don't hold boost for shit. Like major leak. I'm going to retrofit some Supra PCV valves... Should likely upgrade my Cavalier too...

Did you ever "upgrade" your PCV valve? Just wondering if I should be looking into doing this for when the time comes

Revisiting this thread now that my motor is up and running.

I noticed something on my LX9 that seems abnormal and that is a small amount of oil in the mouth of the throttlebody. There are only 2 places that could introduce oil to this area. The PCV vacuum line and the PCV fresh air line (I am using a 3.4 dohc throttlebody that has a non vacuum port to connect the 'intake' side of the PCV that runs to the rear rocker cover).

Earlier in this thread it was determined that the LX9 is not using any kind of 'valve' to limit vacuum to the front rocker cover, I made the assumption that the front rocker cover has an internal baffle to separate oil from air. Could it be the case that it is still ingesting oil through the vacuum line? I notice a good deal of dark smoke out the pipes when I rev it. It is running rich (I am just now working on the tune) and I assumed it to be fuel but it is a bit greyyish in color so perhaps it can be oil as well.

Has anyone noticed a similar issue with their LX9? I am going to double check to make sure that the line to the rear rocker cover is in fact connected to a NON vacuum port. If it is connected to vacuum that very well could be my problem. But if not, and I suspect not, I believe I am ingesting oil into the intake under vacuum. I may install a pcv valve inline to see if the restriction reduces oil ingestion.

The total oil I noticed in the TB was maybe a 1/4 teaspoon. My other thoughts on the greyyish smoke (if oil) is that my motor has been sitting for years - an unknown amount of time in the junkyard and about 1 year on my engine stand - is it possible that the rings are stuck and it needs some good hard acceleration to reseat them?

Thoughts? Similar issues? Resolutions?

edit: forgot to say, that I noticed the oil the day after I ran it. It is not as if I run it, shut it down, and then there is instantly oil in the TB mouth.

2 years ago I had my lx9 swapped in and not too long ago did I notice this on the underside of my CAI right next to the TB...


I also have the same rocker cover as you.


I haven't noticed any smoke out the exhaust but my tips seem to be a little more black then before. But my oil level before oil changes has been a little on the low side.

Did you ever remedy the issue?

The swap was done at 70k and I'm at 117k now..So it didn't start oiling up immediately but I also didn't deliver pizza's in it at first so I racked up a lot of miles between the end of last summer and now.

If it doesn't in fact have an valve should I try some kind of inline one or just swap the rocker cover for a 3400 one(if it fits) so that way I do have a valve?

[young gun]

Oops didn't read through page 2 and the solution :P

But on another note did you end up doing an inline PCV valve?

and also Mars

I just tested a couple stock 3X00 PCV valves and they don't hold boost for shit. Like major leak. I'm going to retrofit some Supra PCV valves... Should likely upgrade my Cavalier too...

Did you ever "upgrade" your PCV valve? Just wondering if I should be looking into doing this for when the time comes

[Starglow]

If it doesn't in fact have an valve should I try some kind of inline one or just swap the rocker cover for a 3400 one(if it fits) so that way I do have a valve?

I used the 3400 valve covers on my 3500 swap, so there shouldn't be any issues with doing that.