Unfortunately, they have been quietly reducing the amounts of zinc and phosphorus in conventional motor oils for quite some time with very little said about it. And the fact is, these motor oils are not compatible with the "dinosaur engines" we are running. Changing up the valve train configuration and type of oil was the death knell for your cam...it's a damn shame you had to find out the hard way. Going with a better oil and a roller cam would be the best preventive maintenance for a future occurrence...I wish you luck on the build.