I wanted to use the J heads I had and do the porting and polishing my self. My research said that if I did this properly I could get about the same flow as a stock set of w-2 heads. After scribing to the head gasket and opening all of the chambers up to an equal size I started on the valve openings and the runners. I did get to the point where I had braised the exhaust runners to put a better radius on them and had opened the intakes up and reduced the valve guides to a minimum. While resculpting the exhaust legs I ran into a thin spot in the casting and hit the water jacket. At that point I decided to look into an aftermarket set of heads, rather than starting over. Yes this is a common screw-up but this is the reality of learning. I will be honest and maybe you can learn from my errors. Pictures of work on the heads are below.