Yes, if the key was missing entirely. It won't install if the slot in the balancer is not aligned with the key, if it's actually there. Without the key, it will eventually work loose and spin on the crankshaft snout.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!