I dont know we run no PCVs on 3 motors 1 SB and 2 BBs.My 12.5 440 has 2 breathers and is new under 5K miles but is street and strip.The kids almost 50 year old 413 ses tons of satreet miles and has never been apart.2 breathers on it too.He runs the snot out of it and has for 9 years.If you balloon a valley pan you need a rebuild period.If its a new motor and does it you have problems.Rocky