Ok, currently I have the push in K&N breathers on my valve covers for my fresh 540. One on front of odd bank and one in back of even bank. After running last year I would get a little mist of oily mist from my rear even bank breather after pushing it hard. Not enough to signify issues but enough to make a bit of a mess in the bilge. I imagine this is a run of the mill issue after reading threads about it from searching but I couldn't come up with a definitive answer. My K&N breathers are un-baffled and there is no baffle under the valve covers except the stud girdles.

So here is the question: What do I replace my K&N breathers with, the nice looking tall bolt-on aluminum breathers or do I go to a catch can breather system? What has eliminated the issue for you guys as I have read the K&N breathers are notorious for this issue?

when the oil gets to operating temp there is a steady mist of oil flying around under the valve cover,this mist finds it,s way out of a breather in the back of a valve cover.

I got tired of fighting this and ultimately went with a catch can system last year.....no more mess.

That's why I use PCV systems on my motors.

So there is no tube going from breather up to flame arrestor? Or pcv system? Before pcv cars used a metal tube venting crankcase down to the road. You must have some way to get crank vent back into intake air. You also get oil smell at low throttle-speed with your current setup.

No PCV or tubing going to flame arrestor. Smell of oil has not been an issue either. I run a custom multi port EFI system and I really don't want to run hoses to my arrestor or into my 2000 cfm throttle body or intake as I would like to go to a clear polycarbonate arrestor soon once it is dialed in. Currently running a 3"x10" SS Babron arrestor. I have tried very hard to keep the top of the motor clean from hoses and wiring.

I was tired of the mess on the valve covers on my Corvette, so I installed a catch can system on each valve cover. A way to improve on the catch can could be to route the vapors off the catch can up yo the spark arrestor

How are the K&N installed? Eddie Young told me to mount the filter 6 inches above the valve cover. This allows the oil to settle out.

Padraig

I ran K&n breathers on my 632 never much below 6000 rpm and never had a drop of oil out the breathers. The breathers were both in the front of the valve covers (wouldn't clear exhaust in the rear).

Yea, the only one that gets any mist out of it is the rear.