Random question....

[s14unimog]

I had never really thought about this that much, until my girlfriend pulled into the driveway tonight and almost stalled her Miata. I just got it for her and she's kind of new to the whole 5 speed action. You ever bog a car down really low, right to the point of stalling it, when you hear that "clack clack clack clack" in real quick recession? What exactly is causing the audible noise? Is it lack of lubrication to the valve train, and you're just hearing the unlubricated mechanical racket of the cam lobes?

Any thoughts?