I have a 541ci RB that I built for a friend break a cam last year. Broke right behind the dist gear, bent a lot of valves. Replaced the cam, timing chain set and all the valves, no other problems. Even the front cam bearing was good.
The cam was only about 6 mo old, a Comp Cams solid lift 650/650. The machinist that I use said that he sees this in round track engines 4 or 5 times a season, rarely in drag racing.

Brian