By swallowing a valve, he means one of the valves that lets air into the cylinder, or exhaust out, snapped off. So you no longer have that cylinder working, plu

By swallowing a valve, he means one of the valves that lets air into the cylinder, or exhaust out, snapped off. So you no longer have that cylinder working, plus you have the valve rattling around against the piston that's still moving up and down. Not good.