At wide open if the carb is the right size, there won't be much vacuum. What valve covers are you using, do they have baffles. Oil is flying all over in there. If not MR Gasket makes a insert for the breather tube. It's like a check valve-baffle to keep the oil in. Works and under 10 bucks for 2.

 

I agree. Another thing is the wrong size PCV valve or an engine with too much blowbuy.

 

I agree needs baffles.

 

The valve covers are Ford Motorsports Tall Aluminum with baffles on both sides. Its a 3/8" PCV line.
I will check on the extension.

 

does this only happen after high RPM pulls? check your PCV valve, it may be sticking. i had a similar problem, mine even tested okay, but after i replaced the valve oil stopped blowing out of the breather.

 

The baffles on those valve covers are still pretty open on the ends...I am having the same troubles..

 

The pcv valve is open when there is vacuum. When you are wide open or nearly wide open (lots of load), there should be no vacuum...which means that the PCV closes. Then where does the crankcase pressure go? Yep...out the breather. That's why you get oil in there.

Most PCV systems use a valve in one valve cover which goes to vacuum. When under light load and high vacuum, the vapors are drawn into the air intake and burned. On the other end, there is normally a hose that runs from the air box or air cleaner. The air cleaner will normally be under a slight vacuum (not a lot but there will always be a little pressure drop) when under wide open throttle. This pressure differential betwen the crankcase and the air box/cleaner will cause the vapors to be pulled into the air cleaner and burned. Take a look at most OEM setups to see what I am talking about. The factory designed them pretty good...well...unless you have a F150 Lightning (2nd generation).

Also, if you have a breather on one side, make sure it has a filter. It can and will pull lots of dirt into the crankcase.

 

well...unless you have a F150 Lightning (2nd generation).

I know what your talking about! I had an '01, with 14lbs or bootst. I miss it badly.

-mike

 

CarCraft magazine did an article about this exact same thing a few months ago on their "Street Sweeper" Chevelle. They found these nifty clamps that seal the breathers to the valve covers so there is absolutely no oil blowing out from underneath them. The clamps cost a good bit (like around $60 a piece), but it sure looked good.

 

I have the same problem with a little K&N breather, if i swap it with the Ford Motosport chromed breather (with holes on the bottom), no leaks...

I saw, some steel mesh in the Ford one, the K&N one is empty.
Should i fill it with the same mesh?

 

Ok so I will get a new PCV valve see what that does. The breather is a push on style with holes under the top with filter media in it.
It happens just at idle as I can see. The bad part is that the oil then runs down to my plug boot then to my header. SMOKE!
If that dont work I will pull the valve cover and see what I can make and reply on my findings.

 

Also; If the breather is saturated with oil already then it's used up and you should replace the breather with a fresh one.

Install a quality PCV valve and new breather and see what you have.