I installed a metco breather but when I got it dyno tuned I was told it was causing a vacuum leak. Is there something I need to do first so I don't get a vacuum leak. I had it installed in place of the oil cap.

I tried search but it wasn't working for me

 

You can remove all of the lines that go to the valve covers to the intake, this will keep it from being a vac leak.

I don't reccomend doing that, I reccomend taking the breather off, there is a reason they're not on the car from the factory.

Ryan

 

So you suggest not even using the breather? But it looks so nice

 

the crankcase needs venting, IMO. id leave the breather on.

 

You need to run the vaccum draw from the opposite valve cover from the Metco only. Plug the fresh air draw and the pcv draw on the Metco side completely.
Now fresh air will be pulled through the Metco, down through the engine and up into the pcv pipe on the opposite valvecover and into the intake to be burned. Should eliminate your problems.
I run the LS6 lifter valley pcv system and a Metco breather. Everything else is plugged. Works great. As a bonus, when you're getting on it the extra crankcase pressure is vented out the Metco.

 

So your saying I should plug the line coming from the throttle body? Do you have a pic or a diagram of your set up?

 

I would like to know also. TTT!

 

Yes plug the line coming from the TB. That's the fresh air draw. Your fresh air will now come through the Metco. Your actual vaccum is coming from the port BEHIND the TB on the intake manifold. Run one pcv line from the drivers side valve cover to the vaccum port on the intake behind the TB. Plug EVERYTHING else.
Now you should have the Metco on the oil cap and one pcv line going from the drivers side valvecover to the intake port behind the TB. Nothing else. See?

 

I get what yer saying!

 

Too bad thats not the right way to do it and you still have a vacuum leak! This has been discussed time and time again, everyone should know it by now. Once you run a breather you have to cap everything off that was once PCV. If you dont, and you run the setup this guy is talking about where you run the breather on the oil cap and run a line just from the driver side valve cover to the throttle body, your allowing unmetered air into the engine which will throw off your air fuel ratio. In order for the engine to calculate the A/F ratio the air needs to be passed through the MAF in order to get the correct reading.

So what you really need to do if your just running a breather is cap off everything that the old PCV went to. So all you should have is a breather where the oil fill used to be, and if you want to fab up one for the driver side go ahead and you will have 2.

Do a search and ask anyone with some good knowledge on the LS1 and they will tell you the same, this guy is telling you the wrong way to do it and he must be running his car the wrong way also. As JRP would say USE THE SEARCH BUTTON!

Hope I helped you both and all Good Luck no burns intended.

 

http://ls1howto.com/howto/geniii/ls6...kpcvsystem.jpg Get rid of all these lines and cap all the holes! The other way is the way old school carb guys do it because they can compensate for the air by adjusting some screws to add more fuel.

 

I just saw this. If you run nothing but a friggin breather, like I have already done, you'll get gunk and crapp built up in your motor because there is no good ventilation.
When I ran breather only I got muddy gunk underneath the breather.
santin04: the pcv valve IS the air meter. It allows a CERTAIN amount of UNMETERED air in to the engine BEHIND the MAF even on a bone stock setup. The engine is tuned for this. By changing to a valvecover breather as your pcv fresh air intake instead of the factory design you are hurting NOTHING. You are simply changing the location of the fresh air draw while simultaneously giving the engine more area to vent during hard acceleration.The reason the factory doesn't do this is because of emissions reasons. That extra venting that comes out of the breather is EPA no-no AIR POLLUTION.
The pcv valve limits the amount of air that can be pulled in umetered. Try blowing on a pcv valve. See? It limits the amount of air you can flow through it. You can blow or suck as hard as you want and only a certain amount of air controlled by the pcv is going to go in to the engine at a certain rate. Once again the engine is tuned for this. When you completely remove the pvc, that's when you mess up your tuning a bit. You will notice a slightly different idle quality.

THERE WILL BE NO VACCUM LEAK. IF YOU KNEW ANYTHING ABOUT PCV SYSTEMS YOU WOULD SEE THAT THE PCV SYSTEM IS A "TUNED" VACCUM LEAK.

I have been running this setup for a long time now and it works flawlessly.

Old school carb crapp is just that...OLD SCOOL....CRAPP!
If you need further clarification, I'll be here.

 

Im still sorry smart guy, but your wrong.

Look at a bone stock LS1 with stock pcv. the entire pcv system is sealed...correct! So the air that has entered the engine and is circulating throughout was metered and calculated by the maf....correct. Oh but wait, whats this little tiny tube on the throttle body above the pcv hose.......it happens to be a fresh air tube WOWWWW. So let me guess all that air that has been metered by the maf, a little bit of that fresh air has been used for the crankcase ventilation, marvelous. But hold on where does that air go that has entered the fresh air tube, it has to get out right? Yeah once it has taken its course, oh WOW it comes out those little valve cover holes where that hard line pcv is hooked up to......and guess what, it goes into the intake can you believe it, it has carried all those little bad guy fumes and all his buddies to be BURNED as part of the A/F ratio that was calculated in the beginning WOWWWWWWW. This protects our enviornment, by burning the bad guys instead of venting them into the atmosphere.


A correct stock pcv system wont work properly if it isnt sealed correctly. The stock pcv system isnt a metered vacum leak either. Its not a vacum leak if its sealed and getting burned up later right.

Try this, if you have a pcv line hooked up to the throttle body, or if its even capped off. Pull the cap or line off the throttle bodys actual pcv hook up, and your engine should bog like all hell because you have created a leak and guess what, its because its unmetered air entering the engine throwing off the A/F.

 

I also never said that a breather alone is the best setup, of course gunk will be built up. I dont expect it to work its way out the breather and on to my headers to be burned hahah. Breathers alone are primarily race setup for drag cars. Short quick races where engine is torn down after the race. The best way would be a vacumm pump, like set up on full duty road race or track cars. Which is tricky to put on an LS1 because of fabrication and price reasons. Or a crankcase evac setup which is cost effective, but wont work properly because of restrictive stock and aftermarket exhuast systems that create backpressure. Open headers or straight pipe to the axle are needed for this which is race only.

Someone find this post and back me up. Thanks all

 

Dude..you've got quite an attitude for someone who obviously hasn't halfway thought thru this simple PCV system. Pull the fresh air hose off the TB and plug the TB hole and plug the valve cover fresh air hose bung. Now stick a breather on the valve cover oil filler and what have you done? You have simply moved the fresh air intake to a different locale SIMULTANEOUSLY allowing more area to vent crankcase fumes under a high rpm, high crankcase pressure scenario.Which the factory PCV system cannot do efficiently.
I never said this was the best way to run a bone stock friggin, panty waisted, worried about some fumes car.
The fellow asked about a vaccum leak and if he could safely run the breather because he liked it. I told him the proper way to do it. I run this sytem on my car my car makes over 500rwhp NA and I have very little oil usage and the crankcase is venting properly. My PCV system works wonderfully and as efficiently as a bone stock one except for emissions which certainly will come out of the breather. But I'd rather have that than a bunch of crankcase pressure and blowby. The proof of this setup working well is the slight oil residue in my intake from the PVC system sucking out oily crankcase fumes. Just like your bone stock one.
Now...the PCV IS a ("tuned")vaccum leak if you don't believe that, SMART GUY, pull the PCV hose off the TB with the engine running and watch the engine idle go nuts even with the factory fresh air hose still plugged in OR NOT. Dang what a miracle.... The air being pulled in through the PCV hose is BEHIND the TB on the intake manifold. This air is not "metered" in the sense you are thinking. If it had a tiny MAF sensor on it's line then the pcv air would be "metered" but it doesn't have a tiny MAF so it isn't metered. The only metered air comes through the MAF and into the TB. The PCV is pulling air behind the TB from outside the engine ,unmetered, hence a vacuum leak. The engine is tuned for this "leak" via the factory PCM. It makes absolutely no difference where the fresh air draw comes from. The ONLY reason the factory routes the fresh air intake for the PCV this way is for emissions reasons not any psuedo air metering.
I know you're thinking the factory fresh air hose air is metered but it really isn't either because it is simply "siphoned" off the sealed, clean filtered air of the intake ducting. it is way too small of an amount of air to affect any metering. Once again it is done this way primarily for emission reason so blow by fumes that reverse up the fresh air hose get sucked back into the engine.

Don't get upset friend, you can test all this quite easily. Route your sytem as I suggested by plugging the factory fresh air holes on the TB and the valve cover. Now put a breather on the oil cap. Did your idle quality change at all? Now with the factory fresh air stuff plugged and the breather on the oil cap, unplug your PCV line from the intake. What happened? Even if you completely close off ALL the factory PCV stuff and run breather only, you will notice an change in idle quality because the engine's PCM is "tuned" for the PCV systems "leak".

If I have to keep explaining this to you I'm going to start thinking either you are not very intelligent or you just like to argue. Either way I'm out. I don't know how I could explain it any better.

And you're right, these discussion have been going on and I've been in them for a few years before you signed up on this board and on LS1.com years before that. The discussions we had way back then aren't even on file anymore as far as I know. This ain't rocket science people...

 

The stock PCV system is not a "("tuned")vaccum leak." Think about it. Where does the PCV system get the fresh air from? It is a sealed system and the fresh air must come from the outside correct? ALL outside air goes through the MAF. The air going from the TB to the valve cover means nothing, because the air that comes from the hole in the throttle body must first go through the MAF and is most certainly accounted for. You will have a vacuum leak if you use a breather and still keep the PCV system, but if you do away with the entire PCV system and just use a breather you should be fine, except for the risk of gunk inside your engine.

 

Very explicite explanation and I run a Metco breather on my car also(3 years now) my car uses LESS than a 1/4 quart betwen oil changes and has even stayed that way since adding a 100 shot of spray.

 

Can't we all just get along?

 

THANK YOU FOR THE BACKUP!

 

Now...the PCV IS a ("tuned")vaccum leak if you don't believe that, SMART GUY, pull the PCV hose off the TB with the engine running and watch the engine idle go nuts

the engine goes nuts because you have just removed the vacuum line from a sealed system hence the reason why it idles eratic

My PCV system works wonderfully and as efficiently as a bone stock one except for emissions which certainly will come out of the breather. But I'd rather have that than a bunch of crankcase pressure and blowby. The proof of this setup working well is the slight oil residue in my intake from the PVC system sucking out oily crankcase fumes.

Ever heard of a catch can to catch that oily residue and prevent oil burning.

The air being pulled in through the PCV hose is BEHIND the TB on the intake manifold. This air is not "metered" in the sense you are thinking

are you crazy any air that is hitting that TB and entering any hoses in front of or behind it has to go through the MAF sensor first, any air period entering the engine has to go through the MAF, what the hell are you talking about

Even if you completely close off ALL the factory PCV stuff and run breather only, you will notice an change in idle quality because the engine's PCM is "tuned" for the PCV systems "leak"

wrong once again, obviously you were the guy in all your discussion years or so ago that your so proud of that made everyone dumber like your doing now. Tons of people run this setup and i have heard no one say anything about a change in idle quality. TUNED FOR A LEAK WHAT A LOAD OF CRAP HAHAHA


SpeedInc must be wrong also then since they were the ones that turned me on this direction when i first started modding. Oh yeah and Larry runs breathers the same on his car, he must be wrong also.

Next time I go for a new dyno tune Im gonna be like OH YEAH MAKE SURE YOU TUNE MY ENGINE FOR MY PCV VACUUM LEAK THANKS GUYS WOW

Your wrong Im telling you man, they ran the same exact setups on carbed cars years ago its the same principle. Carbed cars worked the same way, any air they pulled through the fresh air breather that was circulated through the engine out the pcv had to be accounted for once it reached the carb. Then they would tinker and turn screws to get the A/F correct, because they were metering or tuning for that increase of air. http://home.tiscali.be/be058723/dodge/emis3.jpg

Your lost man go back to auto class read the books twice then try to apply it to the real world. Book smarts dont mean crap unless you have experience. Im done with you and wont read another post off this thread. But feel free to post again so you can make yourself look even smarter.


THANKS TO ALL, NO BURNS INTENDED