Like John said check your oil for the fairy gold dust....lol

Sometimes depending on how bad the bearing is it wont even knock on idle until you rev the motor up even a little, just cracking the throttle.

Trust me I know, ive had it.

If you do have a spun bearing and you still have a 7 bolt more then likely your crank is done for.

Do only way to survive a spun rod bearing is by having a nitrated crank, and thats not a guarantee either.