hmmmm... It could be a worn camshaft or a bent valve or a backed off nut on the rocker..
First thing I'd do is to put a wrench on the nut and see if it is tight.. CAREFUL! don't twist it off!
Then I'd look at the rocker ball to see if it is worn out.
DO THIS.. put your hand on the rocker and see if it has slack in it at full closed/valve... if it does then press on the lifter side of the rocker and see if the lifter is raising the valve as much as the others are.. If not then it is the camshaft that is worn. I have seen push rods go away too.
Now that it is running tell us about the oil a bit more.. What is it that is in there..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist