oil catch can

[Cutlass]

Ok I finally took pictures of my catch can and LS6 valley cover with built in PCV orifice. Favorite parts about it:
*Over engineered. Not only does the LS6 valley cover help keep the PCV system from sucking oil, the catch can will catch any that might make it through
*Removed all those stock PCV hoses
*Clean looking install.

[tatertot91]

agree, LS6 valley cover with a catch can is the cleanest and imo, best way to go

[JayTA98]

cool guys. I just put my catch can yesterday. I will start with the catch can 1st and then maybe one day ill do the LS6 valley cover.

[TransAmX2]

ok guys, i know this has been beat to death, but I just need a little more sence of security on this. I'm installing my LS6 intake, while I'm at it i figured I should do the PCV catch can mod. I have read every post looked at every picture and decided I am just doing the catch can and not the LS6 valley for the time being. All fine and good but so many seemed to have done the LS6 valley cover 1st or also, I'm having trouble sorting out the facts from opinions and GTO's different from F-bodies, I'm in info overload.

Now I understand I can do this;


but there also seems to be a lot of knowledgeable reasons to instal a bereather also.

so I guess I have a few questions;
1) should i install a breather and if so at what point/s in the system?
2) do I need to have an actual PCV valve in the system if I do the catch can mod, and if so should it be mechanical or oriface?

feel free to link away if there is a post that clearly explains this, and I'm sorry if there is but I feel like I'm loosing sanity as I read the constant contradictions on some of the forums.
thanks a ton before hand, as always

[SMWS6TA]

ok guys, i know this has been beat to death, but I just need a little more sence of security on this. I'm installing my LS6 intake, while I'm at it i figured I should do the PCV catch can mod. I have read every post looked at every picture and decided I am just doing the catch can and not the LS6 valley for the time being. All fine and good but so many seemed to have done the LS6 valley cover 1st or also, I'm having trouble sorting out the facts from opinions and GTO's different from F-bodies, I'm in info overload.

Now I understand I can do this;


but there also seems to be a lot of knowledgeable reasons to instal a bereather also.

so I guess I have a few questions;
1) should i install a breather and if so at what point/s in the system?
2) do I need to have an actual PCV valve in the system if I do the catch can mod, and if so should it be mechanical or oriface?

feel free to link away if there is a post that clearly explains this, and I'm sorry if there is but I feel like I'm loosing sanity as I read the constant contradictions on some of the forums.
thanks a ton before hand, as always

No problem....I've taken your pic and cleared some things up.

You can run a catch can with or without doing the LS6 VCT mod.

This pic is for what you are wanting to do. (Keep stock PCV setup and install a Catch Can)

[SMWS6TA]

OP, this thread may help you.

It explains the differences between the OEM PCV and the LS6 mod

http://www.ls1.com/forums/showthread.php?t=156010

[TransAmX2]

No problem....I've taken your pic and cleared some things up.

You can run a catch can with or without doing the LS6 VCT mod.

This pic is for what you are wanting to do. (Keep stock PCV setup and install a Catch Can)

Thanks SMWS6TA, feeling a lot better about it now, so is the breather the next step if you want the crankcase to "breath" easier or is it not a good idea for some reason?

[SMWS6TA]

some add it, I did not because the LS6 VCT has the PCV on the underneath side of the tray making it internal. It still does the job of releasing crank case pressure/vapors just not external like the OEM style.

Putting a air breather on with a good filter can't hurt your engine if your worried about that.

Adding the catch can just filters the oil form the crank case vapors from the blowby that is from the pcv.

[TransAmX2]

some add it, I did not because the LS6 VCT has the PCV on the underneath side of the tray making it internal. It still does the job of releasing crank case pressure/vapors just not external like the OEM style.

Putting a air breather on with a good filter can't hurt your engine if your worried about that.

Adding the catch can just filters the oil form the crank case vapors from the blowby that is from the pcv.

understood, the breather part confuses me a little still;
- it doesn't make sence to put it on the "clean side" (green) because that would already be taking in clean outside air (no advantage except maybe a super-slight pressure increase before the TB because it's drawing from the vent not through the cars air filter).
-If you put it on the dirty side before the PCV valve then little to no pressure would go through the valve itself, making it and everything after it useless.
-if you put it between the PCV and the catch can again the pressure would be lost at that point and all that would collect in the can would be whatever oils got trapped or condensed on the walls of the tube/filter and ran down into it.
-after the can would trap the oil and basically vent the air instead of reintroducing it into the intake, but it would allow air to bypass the mass air flow and TB.

I feel like i'm missing something and too tired to put my finger on it.

[Cutlass]

You can use a breather instead of the clean side hose between the TB and passenger side valve cover (the green hose in the drawing).
HERE'S the difference in the 2 setups:
With a breather (and catch can on the dirty side), you eliminate all chances for oil mist to be ingested back into the intake manifold through the PCV system. Which means your TB and intake manifold will stay cleaner and drier. One possible downside could be oil misting out onto you valve covers through the breather.

Now you might be wondering how the oil mist is gonna travel backwards through the clean side of the PCV system. Well, that can happen at high rpm WOT runs where piston ring blowby is greater. That excess blowby builds more crankcase pressure and can overload the normal PCV system flow. Meaning there is more air in the crankcase then the little PCV valve can flow/suck out. So that excess air backflows out the clean side of the pcv system.

[TransAmX2]

You can use a breather instead of the clean side hose between the TB and passenger side valve cover (the green hose in the drawing).
HERE'S the difference in the 2 setups:
With a breather (and catch can on the dirty side), you eliminate all chances for oil mist to be ingested back into the intake manifold through the PCV system. Which means your TB and intake manifold will stay cleaner and drier. One possible downside could be oil misting out onto you valve covers through the breather.

Now you might be wondering how the oil mist is gonna travel backwards through the clean side of the PCV system. Well, that can happen at high rpm WOT runs where piston ring blowby is greater. That excess blowby builds more crankcase pressure and can overload the normal PCV system flow. Meaning there is more air in the crankcase then the little PCV valve can flow/suck out. So that excess air backflows out the clean side of the pcv system.

ok, so if i install a breather on the "clean side" there is really no reason to connect the clean side to the throttle body anymore correct?

[Cutlass]

yep thats right.

[TransAmX2]

so any additional breathers (any installed on the "dirty side")would be replacing the PCV system entirely correct? Basically venting the entire crankcase to outside air, no more manifold vacuum in the equation?

[Cutlass]

yes. I wouldn't do it that way, but yes that could work. I don't think that would work as well as vacuum sucking out the crankcase through a PCV valve. If you really don't want a PCV valve, you could make an really old school draft tube.

[TransAmX2]

ya, i think I have a good hold on it all now, I think the main thing that got me all twisted up in the first place was this thread:
http://www.ls1.com/forums/showthread.php?t=81389
and some of the conflicting info in it, partially because it was initially based around a GTO system, and some people are just running breathers without PCV on the higher HP cars.

[TransAmX2]

here's the finished product with the LS6 intake, LS1 valley cover/ coolant lines, Oil seperator catch can