360 Problems

I have a 71 Scamp with a 360 in it that I bought this spring which was supposedly just rebuilt. It has a mild cam and I have not been able to get it to run the way it should. I did replace the intake because I thought that was part of the problem and sure enough it ran much better. That is until yesterday!
Started it up yesterday and it sounded horrible, a minute later it smoothed out. Then it sounded like metal on metal! All of a sudden it starts blowing smoke out of the drivers side exhaust. Barely made it back in the garage. I pulled the intake and valve covers and everything appears fine, but I got a bad feeling there is something going on under the drivers side head. Also I drained the oil and it doesn't look bad at all. Any suggestions before I pull the head?