motor question?

I have a 65 dart and a 340 auto and here is my problem last week me and my youngest went to go get gas and on the the way home a problem arose. I used the manual shift mode and got on the car a little hard and after that I know have the breather puffing out oil. I took the valve cover off and everything looks ok but if I turn in over I heard a hissing at the back of the rt head. Put the valvecover back on started it and reved it and white smoke comes out the rt tailpipe so any ideas?

let me know thanks:scratch: