Is a vent in your valve cover a huge vacuum leak?

[92BIGREDBEAST]

Im having some issues with the idle. I have the stock PCV valve in the rear of the lower intake and a valve cover breather in the pass side valve cover. The breather has a tun of vacuum to it. Is this a giant vacuum leak? I had it on my old set up like this but now the new set up wont idle very good. Is the breather in the valve cover necessairy? Is this un metered air going thru the motor that the MAF doesn't adjust for? Any help is good help. Im at a stand still as of now... Anyone want to stop over to check it out let me know, Im in Catskill 35 min south of Albany! I feel like this....

 

[cledusdtrucker]

you don't need the pvc hooked up just block it from the intake and throw another breather on where the pcv vent was its all for emissions

 

[Teal93LX]

If your PCV is working the breather is not needed all the crank case pressure should be released thru pcv. I doubt the breather is causing a vacuum problem it not leaking any unmetered air in to the intake manifold. Good luck with it tho you cauld do some testing woith a vacuum gauge or use smoke to pinpoint the leak.....

 

[MaximumRisk]

Having the PCV hooked up and a breather on your valve cover is a vacuum leak. Either plug the PCV line and leave the breather or leave the PCV and remove the breather. Be aware that if you remove your PCV valve the car will not pass inspection

 

[EHA Racing]

You need some sort of way to relieve crankcase pressure. Either through a PCV, vacuum pump or crankcase evac system. A breather will help from creating too much vaccum and sucking in oil and seals, or helps push out extra pressure if the PCV system is not efficient. Having vacuum at the valve cover hole is a good thing which means the PCV is doing it's job.
Now just the opposite, if you have pressure at the valve cover hole you have a problem of some sort. Inop PCV, ring problem, damaged piston, bad valve guide....... You never want pressure there, only vaccum.

 

[ShelbyGT]

sounds like your pcv is bad

 

[EHA Racing]

sounds like your pcv is bad

?????

 

[dsblk93gt]

I didn't realize you had a breather on it, I must have misunderstood I was half asleep earlier today. Technically with a breather you are introducing unmetered air into the engine. Any air not metered is unable to be adjusted for by the ecu so it will run leaner at idle and low loads. I have never had a car that had a real strong pull on the valve cover, you definitely don't want pressure coming from it. I usually would say either run a PCV closed setup or delete PCV and run breathers but not both. Check with it closed off to see what the A/F is and then with the breather closed off. You should be able to richen the idle a/f up to compensate for the breather though.

 

[ShelbyGT]

yeah, on a computer car the system must be closed, meaning no breather in the valve cover that just vents to the outside air.

the breather tube must be hooked to the air box or the result is a vacuum leak, and the vaccum leak causes the ecm to try to compensate and fight itself and the iac which causes the irratic idle

you can get away with a breather on the valve cover and a pcv on a carb car because you can compensate in the idle adjustment

so its either only valve cover breathers or only the stock pcv setup, no combinations

 

[EHA Racing]

Ahhh, the breather was open to the outside air?? I thought it was hooked into the air intake like they come factory. My bad, I was wondering why you guys were saying to get rid of it.

 

[92BIGREDBEAST]

Thanx guys. It seems like when i block off the PCV valve vacuum to the upper intake the car runs very good, idles fine.. When i put the pcv back in the lower intake where it belongs,the car starts to stall out. Even when i block off the valve cover hole... WTF... Can i get rid of the PCV hole in the lower and put a PCV in the valve cover and use vacuum from the powerpipe? I think there is alot less vacuum from there, rather then drawing from the upper. On my old set up the car ran perfect with the open valve cover breather. Now i have a QH and new tune and i am having problems... Im gonna play with the tune some more before i change the set up with the PCV....

 

[ShelbyGT]

i wouldn't play with the tune

also, a pcv does a much better job of evacuating the crank case that just breathers, so i wouldn't eliminate that.

it sound like you pcv wasn't working proplerly on your old setup, thats why the breather didn't affect your idle

i would try running a breather tube into the powerpipe, similar to how the breather tube runs into the stock airbox

 

[dsblk93gt]

Keep the PCV and run a tube from the vc to the powerpipe.

 

[cobra20sc]

Keep the PCV and run a tube from the vc to the powerpipe.

+1 but to clarify, from PCV to powerpipe downstream of the mass air meter. not sure if your powerpipe has another place for a fitting here (on the bottom side is the bypass line). i had to add one on mine. as i mentioned before, i have tubing run from both valve covers to the powerpipe. at full bore under boost conditions, the vacuum upstream of the supercharger in the powerpipe helps to pull/relieve the pressure from the valve cover . . . .gets worse with ring wear. use an oil separator of course. this is similar to the setup on today's supercharged cobras.

on a fuel injected motor, closed system is always the best bet.

 

[dsblk93gt]

+1 but to clarify, from PCV to powerpipe downstream of the mass air meter. not sure if your powerpipe has another place for a fitting here (on the bottom side is the bypass line). i had to add one on mine. as i mentioned before, i have tubing run from both valve covers to the powerpipe. at full bore under boost conditions, the vacuum upstream of the supercharger in the powerpipe helps to pull/relieve the pressure from the valve cover . . . .gets worse with ring wear. use an oil separator of course. this is similar to the setup on today's supercharged cobras.

on a fuel injected motor, closed system is always the best bet.

Yea after the MAF, sorry I should have clarified that. A "shop" installed the line from my friends cars to the adapter BEFORE the MAF!! LOL Works awesome with oil misting on the MAF lmfao!!!!:smash: