How are LQ4's pcv system set up?

[BlueZee28]

I am trying to get everything buttoned up on my motor this week so my tuner can come over on Saturday for a test fire, and I thought I had the pcv setup down pat when I went over to my friend's house who has an LS1 and looked at his. His LS1 had a nipple on the driver side valve cover, which ran a hose behind the intake to another nipple on the back end of the passenger side valve cover, and then a 2nd nipple on the passenger side cover (front end) ran to a catch can then to an outlet on the intake manifold right behind the throttle body. Looked simple...Then I went back to my block and noticed my passenger side valve cover has only ONE nipple on it, the forward most one that goes to the catch can. So now I'm not sure what you're supposed to do with truck motors/valve covers. What do you run to the driver side valve cover? I did see an outlet on the intake on the drivers side, about symmetrical to the outlet on the passenger side. Are you supposed to run a hose from the intake all the way to the back end of the driver side cover, and then just run the one hose from the passenger side cover to a catch can and back into the intake?

Pictures for reference:

Passenger side valve cover (only one nipple)








Passenger side cover again, with the catch can








The other outlet on the intake manifold I was talking about

[straightaxle]

the hose from the valve cover is supposed to be hooked to that barb on the throttle body. unless there is some advantage of doing it this way

[txarkitekt]

First things first--do not base a truck's PCV from a cars. Their PCV routing is totally different.

Take the back driver's side valve cover and tee it with the front passenger valve cover and route it into the catch can. Then take the outlet of the catch can and route it to the pass side of the intake manifold up by the TB.

[BlueZee28]

So BOTH the valve covers need to go to the inlet on the can? Hmmm. Where do you find a "t" for that kind of hose?

And do I have at least the outlet hose on the can correct, or does it need to go to the metal nipple actually ON the throttle body??

[txarkitekt]

So BOTH the valve covers need to go to the inlet on the can? Hmmm. Where do you find a "t" for that kind of hose?

And do I have at least the outlet hose on the can correct, or does it need to go to the metal nipple actually ON the throttle body??

Ok...the driver's side valve cover hose goes into the top of the intake to the PCV, right? If so, this is the "dirty side" of the PCV. The passenger side valve cover hose goes into the TB (my mistake on not describing it properly the first time--the cable style TBs have the barb, the DBW TBs have it on the intake) is the "clean side" of the PCV system. This is where even I get confused... Now--you could actually LEAVE the passenger side tube from the valve cover to the TB alone...I THINK. This would leave the driver's side valve cover hose to the inlet of the Catch Can...and the outlet back to the top of the intake where the PCV actually is. I wish that I had the motivation to go out to the garage to look at my truck...but it is cold as balls outside in the garage and I don't wanna take the engine cover off. Anyone else wanna comment?

[BlueZee28]

If someone could get a picture for me that would be awesome, I am having a hard time picturing how it should look.

[txarkitekt]

Hey Nick--been going between this thread and the other on on Tech...and this is what you need to do:

Here I talk about leaving the passenger side valve cover connected to the nipple on the TB...

Now--you could actually LEAVE the passenger side tube from the valve cover to the TB alone...

Then take a hose from the driver's side valve cover to the inlet side of the Catch Can, then a hose from the outlet of the Catch Can to the passenger side of the intake.

I explained this here KINDA...but since you are running a car style intake versus a truck style, the PCV port into the intake is different. On the truck, it is on the top. On the car, it is up at the front on the passenger side behind the TB.

This would leave the driver's side valve cover hose to the inlet of the Catch Can...and the outlet back to the top of the intake where the PCV actually is...

And since you have the emissions crap taken out, just plug the brass nipple on the driver's side of the intake behind the TB. That should get you the correct routing.

ALSO--that oil/water separator thing you are using for a Catch Can is not gunna work and is not a real Catch Can. Sorry to say...but you will be blowing-by it all of the time and it will fill up in a few days. Go ahead and get a Catch Can from Saikou Michi, AMW, or RevXtreme.

[Sleaper]

Something similar to this except you don't have the rear port on the passenger side to deal with:






'clean' and 'dirty' are non-technical names for the two sides of the PCV system. Clean (air)= System Input, Dirty (air)= System output


The clean side connects at the throttle body and valve cover for a N/A LSx. This side is designed to flow fresh filtered air from the air intake (atmosphere) into the engine crankcase.

The dirty side connects from the valley cover or opposing valve cover to the intake manifold plenum chamber (engine vacuum).

Blowby can flow out the clean side when dirty side flow is insufficient to overcome blowby production.

**All above information courtesy of 405HP Z06 on LS1tech**

Here is the thread that this was taken from:

My catch can routing ok? - LS1TECH


+1 on getting a better catch can.

[BlueZee28]

So will I still need to get an actual PVC valve and put it on the driver side valve cover?

[BlueZee28]

Nevermind, I saw your diagram when I went home on lunch break. I couldn't see it on my phone earlier because the screen is so small haha

I appreciate all of your help guys! And I ordered a revxtreme can on my break too lol