fresh 318 questions

If the battery is down, that may be "normal" for a couple of minutes, but I would not take chances. If you are breaking in a fresh engine, especially a new cam, you can't be worrying about the charging system. So until you get the cam broken in, the engine fully warmed, the oil system/ pressure checked, etc, I would simply unhook one of the field wires at the alternator, which SHOULD stop it from charging.

Then as things get to be "more normal" you can post back and we can figure out t he problem.