A cam can quite easily be broken if it was manufactured incorrectly. Bad casting gives them weak spots. (an air pocket inside the metal).
This type of incident is more common in the old push rod engines probably because there is more load on the cam. I know of a few people who have demolished $10,000 engines as a result of this.
If I were you, Iíd grab another head, reco the thing, and clean up the ports while your at it.
As for a cam, grab a s/h one (For $50), or better still, something like a crow #2.
CAUTION: Slippery When BOOSTING!