Most people say that the Breather valve on the valve cover allows "FRESH" air to go into the crank case. However, I don't see how that is possible. Since blow by gases come out of the breather valve on the valve cover, how would you force fresh air into it?

Also from my understanding, the breather valve on the valve cover allows the blow by gases to go back into the intake system (For emissions purposes only). Is this correct? Because My friend took his car to an emissions place and he had a filter on the valve breather and the guy said that a hose must be connected there to the intake to reroute the blow by gases back into the intake stream so we don't pollute the environment.

 

the breather and pcv allow gases to come up through the engine and into the intake system (like bad oil gases)

those cheap k&n breather filters are a waste...they hurt more than help because the vacuum created by the intake system is needed to pull the gases up. you'll lose hp with them in place.

a sealed catch can is a good idea because it retains the vacuum while keeping the oil sludge in a seperate container (versus feeding it to the engine, which lowers octane and could cause detonation).

the pcv valve (to answer your other post) is like a check valve. it's got a spring loaded "piston" that will open as the suction increases. when you put your finger over the pcv vlave (to check and make sure it's still moving) you are closing the vacuum and causing the piston to go back down.

 

you may have mis-heard the guy,

the hose must connect to the intake pipe and connect to the top of the rocker cover.

this is where the 'fresh' air comes from. some people replace this pipe with a filter.

the air then goes into the crankcase, and gest sucked into the intake to be burnt. this happens on hte intake manifold - nothte intake pipe - after it has gone through hte PCV valve and maybe a catch-can.

HTH,

t..