[Syonyk]

And most older engine will float the valves and, assuming nothing collides or comes apart (floating valves isn't good for the rest of the valvetrain), self limit that way.

But almost any engine with electronic ignition (so early 80s or later for a standard car or motorcycle, with plenty earlier having that feature) will cut spark to control RPM as needed. Unless you just start getting ignition breakup at RPM (not enough dwell time for the coil).

[dotancohen]

I actually saw a small block Chevrolet or Mopar (don't remember which) dent the hood this way. I suppose the rocker rotated when the valves floated, when the valve broke the stem went right through the valve cover. Funniest thing I'd ever seen at a drag strip.

[gonzo]

with nothing resisting the crankshaft, the rods will ensure a ton of stress at the bottom of the “power” stroke, and will shortly depart the earth.

[winrid]

Most modern ECUs won't cut fuel intermittently but will instead just hold RPM steady at some defined max speed. However, I guess you'd have to be pretty unlucky to have this happen with a drive by wire setup...