Just as a follow-up, I have not had a chance to do a compression test yet, but I did get a chance to change the oil. Went from full synthetic 5w-30 to MaxLife synthetic blend 10w-40 (I know the owners manual says not to use it, but I have 150k+ and I'm pretty sure its no longer within factory tolerances) and my oil consumption was cut dramatically. Now after 100 miles my catch can only fills about 1/4 of the way...still way too much, but a heck of a lot better than overflowing after 100 miles.

 

You're saying just changing from 5-30 to 10-40 has a dramatic change on oil flow out of the PCV? That's interesting. How large is your catch can that it would fill in 100 miles. I bought a small air compressor water seperator at Harbor Freight for $7.99 and installed it. I ran 700 miles to Houston over the weekend and had about 2 tablespoons in it when I got back. Engine is low mileage. It was oil and water mixed.

 

I have an AMW catch can on my 05. It has the fixed orifice PCV valve. I empty it once a month. I get a couple of OZs of oil out of it. It has been on there 4 years with no issues.

 

I'm still trying to understand this "fixed orifice" thing. I thought the variable orifice was there for a reason. GM isn't the only one using the fixed orifice on the valve cover. There must be a maintenance interval to remove the rocker cover to clean the PCV inside because it will eventually get gunked up.

 

I ran the fixed orifice PCV for a while and I got the same amount of oil in my home made catch can as with the spring and plunger PCV. Then when I upgraded from my home made catch can to the AMW the setup whistled with the fixed orifice PCV and drove me nuts so I swapped back to the original PCV.

 

Mine has never whistled. The guys at AMW told me sometimes they would do that but mine never has. 04 and up the PCV is made in the valve cover and is not removable. It has no moving parts and is not serviceable.

 

If a fixed orifice(mounted in rocker cover) has no moving parts it doesn't fit the definition of a valve. A PCV is supposed to move from fully closed to partially open to fully open depending on crankcase pressure, intake vacuum or intake pressure(backfire). A fixed orifice doesn't do these things. It just stays open all the time. In this day and age with the EPA controlling emissions so closely I can't figure out why they went to an unregulated system.

 

The fixed orifice PCV was GM's attempt to control excessive oil consumption, they have a TSB in reference to this. I tried it and it didn't work for me lol.

 

I'm not surprised it didn't work for you . How could it? It's just on open port. A PCV is not a catch can. It is only supposed to regulate crankcase pressure(air flow containing oil and water) not reduce oil consumption due to excessive blowby. The more I think about this and see the smegma in my catch can(canister is clear plastic) the more I believe vehicles should come from the factory with a catch can, but then I think they should come from the factory with underdrive pulleys too so what do I know.

 

Catch can n00b question - where do those two black hoses coming out of the catch can plug into on a fixed orifice PCV system? Does anything get removed from the engine when installing these, or just relocated?