On my 99 Z28, it appears that the nipple on the rear of the pass. valve cover goes behind the intake, and ties into the line coming from the driver valve cover. Am I wrong? It defintely goes backwards, and touches the other line. Seems to have some kind of wrap on it.

 

Why are yall so scared of just putting a breather on your valve cover and doing away with the pcv? The ls6 has no PCV right? It is just vented into the valley under the intake. If you put a breather on the valvecover it will get fresh air as well as releave pressure.

I am running a metco breather in my valve cover. I removed the PCV from the plastic hard lines and installed a small breather on the end of that hose. Now Both valve covers are vented. I will go take some pics and post them up.

Brad

 

It is true that on the stock setup, the PCV sucks off of both sides - the line from the DS does come around and tie into the valve cover on the back of the PS. The front line on the PS to the TB is the fresh air inlet.

The problems with the stock system are two-fold:
-At part throttle, when there is vacuum on the PCV (the only time there is vacuum on the PCV - none at WOT) it sucks oil up into the intake. The only good fix that seems to work is the catch can. However, my new engine doesn't pull anything (with an LS6 valley cover), so I took mine off. It seems that this varies from car to car for some reason.

-At WOT, the check feature built into the PCV is actually pushed shut because there is not vacuum in the manifold at WOT. This allows pressure in the crankcase to rise and can cause the oil that comes back up the fresh air inlet from PS to the TB. I solved the oil going to the TB by taking off the line and plugging the TB connection, then putting a small breather filter on the line. The problem then is that the filter will drip some oil after lots of runs at WOT.

You can't tee into the same catch can that the PCV goes to for the fresh air inlet line or you will be short circuiting the entire system - basically the line from the intake side will suck through the PCV and the catch can and then from the fresh air inlet line - you will get little or no suction on the crankcase.

Some have used the valve cover type breathers on one side to solve the pressure build up. That seems like it would work if done properly in conjunction with the PCV (like the old school motors did).

Here is how I would do it if I were keeping a stock type system (BTW, I am switching to a race type crankcase evac system): I would put one of the new K&N type breathers on the PS that fit on in place of the oil fill cap. That would provide the fresh air inlet, so I would plug the TB connection and both connections on the PS valve cover. Then I would connect the PCV from the manifold, via a catch can, to the DS valve cover connection, or the LS6 valley pan if you have it. This will provide a good circuit for air while having adequate WOT pressure relief. If you look at all old school engines, they have the same thing - PCV from one valve cover, breather on the other.

Obviously this is just my 2 cents! I have done a good bit of research on the subject and it seems this should work well for a mostly street driven engine.

My car spends most of its life at WOT, so I am designing a header type evac system (one that also allows me to keep the PCV for my little bit of street driving). Once I get it done, I'll post up how it works out.

 

Here ya go

 

blk02ws6: Thanks for the awesome post. I think I will keep a similar stock setup. Keep DS and PS rear lines together, go to catch can and then into intake.

I like the idea of a breather on the oil fill cap, or the front PS nipple. I think this is what I will go with.

Thanks.

Anyone else?

 

How many race motors do you see with a PCV? A vaccum pump is cool and has been shown to increase hp. A crank case evap only works with OPEN HEADERS. A breather is sufficient in most applications.
The PCV is more of an emmisions freindly breather. The vapors that escape the motor through the PCV are then burned in the combution chamber instead of being introduced directly into the atmosphere.

Brad

 

If you do away with the PCV there is no need for a catch can.

Brad

 

The advantage of taking a suction on the crankcase is that it helps the rings to seal and it helps prevent gasket leaks. At part throttle, where most street driven cars spend most of their time, the PCV pulls a slight vacuum on the crankcase to do just that. It will also help fuel economy a little at cruise cause the pistons don't have to work against pressure if there is a vacuum on the bottom of them - so you get a little more work for free basically. This only works at cruise though - which is why I am going to a setup that gets that advantage at WOT as well.

What you have done with the breather is good for letting fresh air in, and good ventillation for WOT when the PCV isn't sucking - but you have taken away the advantage of the suction at cruise. If it were mine, I would leave the breather just like you have it, but reconnect the PCV with a catch can to the DS valve cover. Like I said before, just my opinion.

Oh, and the LS6 does have a PCV that sucks from the valley pan.

 

General, you should read a little closer what blko2ws6 said.... "You can't tee into the same catch can that the PCV goes to for the fresh air inlet line or you will be short circuiting the entire system - basically the line from the intake side will suck through the PCV and the catch can and then from the fresh air inlet line - you will get little or no suction on the crankcase."

You just said "Keep DS and PS rear lines together". Don't do that. It would be incorrect.

What blk02ws6 said is if youre gonna run a breather, you would cap both tubes on the passenger valve cover and the TB tube where they used to be connected to. The only thing going to the can would be the hose from the PCV.

Know what I mean?

 

Fastt - He isn't talking about both the suction and fresh air inlet lines going to the catch can - however, I think taking a suction off of both valve covers will still short circuit the system. The connection that sucks off of the PS rear will just pull from the fresh air inlet (or breather) on the PS instead of pulling air from the crankcase. That is why I would go with suction on one side, fresh air on the other.

 

He said he wants to connect the PCV the PS rear tube together and then go to the catch can. Why?? That doent seem right.

The only thing going to the can should be the PCV hose... Right?

Then, get fresh air however you like.... like stock, or a breather in the oil fill location and cap the PS tubes and TB.

 

I think he means keep the stock PCV suction (it takes a suction off of both the PS and DS rear connections) and run that to the catch can and then the PCV. So the only thing going to the catch can would be the PCV suction hose. If you look at the stock system (hard since it runs back around where you can't see it) it connects to both sides then to the PCV.

You are right though that it isn't the best situation cause the PS suction will just pull the air from the PS fresh air inlet (or breather) and short circuit the crankcase.

Know what I'm saying?

 

Thanks, I was not sure on that. You answered my question! Someone had posted earlier that there was no valve. That is why I posted that

Definately was not trying to flame either. I simply wondered why most folks did not want to completely remove the PCV valve. You answered that too Instead of saying its a no no with no explaination.

BTW you might want to look into a vaccum pump. There are a few manufacturers that make an electric one that does not need to be driven by a pulley. This would be a pretty cool set up. Then you will be Pulling vaccum from the crank case at all times. Not just when there is vaccum in the intake

Brad

 

No flame taken I woud love to do the vacuum pump, but I am poor these days! That setup is freakin expensive! The electric ones have been tried and don't really pull the vacuum needed to do much good (as far as gaining horsepower).

So I am going the header route with a twist! I don't drive my car a lot on the street - I mostly race my car at the track with open exhaust, so the header system will work for me there. I plan to put in a simple isolation on the header lines that I will close when I cap my exhaust for street cruising. The PCV will be left in place to take over then.

I have it pretty much figured out, just have to gather up the parts and get it installed. The only question that remains to be seen is if the little isolation valves I have found are gonna hold up to the heat of the exhaust. They are rated at 450 degrees, but only time will tell how long they last.

The whole system should cost me about $80 plus welding labor for the header connections.

 

I am sure you thought of this but try to mount the valves as far away from the header as possible. Might help them to last a little longer n keepum away from the heat.

I read about that electric vaccum pump in a magazine. I do not beleive much that I read in magazines lol. But they claimed a 25hp or so gain from hooking up the pump while on an engne dyno. I plan on doing some research before spending any cash on that tho. Let me know how your system works out!

Brad

 

Do you know the name of the pump manufacturer? How much is it? I would like to see that. I'll let you know how mine works out. Thanks!

 

Fastt Gunn: On the stock setup, both the driver and passenger rear lines go to the PCV valve and into the intake. They are connected behind the intake manifold. The only fresh air inlet is the one coming off of the throttle body to passenger front nipple. I believe this to be true.

BLK02WS6: I can dig what you are saying about the passenger rear only drawing from a breather on the passenger front. My question then is, Why doesn't the stock setup only do the same thing? Essentially, all the breather would be doing is replacing the hose on the throttle body as a fresh air source. I guess I can't figure out why GM would connect both rears, with the intake so close on the passenger side?

Thanks again guys, this is a great thread.

 

I didnt take the stock intake off... the shop that did my Heads / Cam install did. The stock plastic piping went with it. I would have never guessed that rear tube was routed with the PCV. Doesnt seem logical. Hmmmm... not sure if Im gonna change mine or leave as is. Seems to be working OK.

Sorry if I confused things

 

Fastt Gunn: I was confused in the beginning as to why you set it up the way you did. Now I understand. Not to flame, but some of these shops that do this work...grrrrr...... There is a kid at work that just bought a 2000 SS for 18,000. Has heads cam, etc.... Got it on a Friday, Monday he brings it into our shop. "It makes a funny noise and runs really rough. A compression check later, found that no compression on #7. We take the head off, broken valve spring. Examine the head. These guys hand ported this head with a carbide tip on a die grinder or something. No polishing. It was scalloped. Looked like fish scales. Well, we look a little closer, chunk of aluminum missing around valve guide, with a crack coming from it, that is going to chunk off more. They tok off so much material around valve guide that they weakened it to a point of failing. Also, the EGR was left in its original location including the stock EGR hose, even though this shop put on a new intake manifold that didn't provide for the hose. So, the hose was just hanging out there.

Supposedly all work was done by a sponsor of this board...........

 

I don't have any idea why the engineers designed the PCV with the fresh air inlet and one of the suctions right next to each other - doesn't make any sense to me - but then,that isn't the first time I've said that!