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Has anyone thought about installing a '70's type pcv valve to cut down on the oil blown out the breather?

without coffee being consumed so far today / IE foggy brain..... Here is my 02 cent ideas;.......using a PCV valve, is a bad idea, because if it go bad, and blocks the over flow, pressure will build up in the engine, and could blow out the front/ prop seal, which dump all of the oil on the windshield. If you look on all standard “Cessna / piper" airplanes engine install, you will see breather tube has a slot cut , just up from the end “i think it is called a whistle slot” so if the end of the breather tube ices up, their will not be a build up of pressure,.............
also I THINK, I remember some thing about the VANS R.V. Forum guy talking about aiming the breather tube toward the exhaust, so the drops of oil will burn off......
good day / rick............IMHO-IMBW,,,,,,i my humble opinion,i may be wrong

...you may not be wrong...so why be humble???

Installed a one way valve system from the breather tube into the exhaust pipe on my RV6.
Worked perfectly with absolutely no oil on the belly after. Every 100 hours or so, remove to clean to make sure it wasn't clogging (which it didn't).
I THINK Anti-Splat sells a complete system. People who had problems with it never removed it to check and clean. I'd absolutely install another.

Joe Gibson

The only credible reason I've heard not to do it is that the oil blown out the breather is a diagnostic of crankcase pressure and of you get rid of it somehow, you have no idea if your blowby skyrockets.

That's why I collect it in a separater and measure the amount along with oil added. A home made seperater using a Ball jar calibrated in oz. At 300 hours I'm showing about 6 - 8 oz. in 25 hours.

Some aerobatic planes have the oil vent line run through a tube to exit the fuselage near the tail wheel (eg extra 300), and some of them collect the oil overflow into a plastic coke bottle (the liquid kind of coke). This eliminates the oil smear on the belly.
On my Sonex with Aerovee, I ran a flexible tube from the end of the aluminum oil breather line down the firewall and out the bottom air exit of the cowling then down the left main gear to exit the oil right behind the axle. No more belly oil. Just put a pan or piece of cardboard on the hangar floor to catch the dripping oil after each flight.
Ron
Legacy Sonex with aerovee

Why re-invent the wheel? You can make an air/oil separator like OneX 107 describes above or get something like Aircraft Spruce's air/oil separator for homebuilts, which return liquid oil to the engine and vent the crankcase fumes overboard (very common in certified aircraft). With either be sure to run the exit tube low enough so the breather fumes do not condense onto the belly. See: https://www.aircraftspruce.com/catalog/ ... ilbreather

OK, I can not resist!! I too have an oil 'problem' on Sirpeedee,now with 43.6 hrs tt, and engine broken in well, and have experimented with 1/2 in dia overboard tubes, and now with 7/8 dia tube. I am in the process of doing two things, first decreasing the angle of the cut at the end of the tube in an attempt to lower the negative pressure on the tube,, leaving it at the same level below the firewall. secondly, and maybe more important, the oil mist is hot as it comes out of the engine breather, and into the seperator (a salvaged part 91 item). since the AeroVee is pretty close to the firewall, and the seperator has to be mounted pretty high up so as to drain back into the LH rocker box, it surely runs too hot, and the mist never condenses. someone, somewhere, mentioned that if the mist isnt cooled, it will never condense the oil to be collected and drained, but will just blow it overboard, where it will condense as, of course, 'oily belly syndrome'. So, today, I have installed a cold air source to blow on the seperator to attempt to get the mist to cool and condense prior to going overboard as non oily mist, or just air (I hope)! I do like the behind the axel overboard tube, and I had forgotten that over the years. However I will try this setup with cold air blast tube, before resigning myself to the behind the gear solution.. As I type this, I wonder if the behind the gear solution deposits anything on the flaps, and how does that set up behave, oily deposit wise, with the pant covering on the MLG?