Ok So My 1999 Mustang Cobra Is Making A Horrible Knocking Noise In The Motor, Sounds Like There Is Something Lose Inside Somewhere, When I Put My Hands On One Of The Valve Covers Is Like I Can Feel It Hitting It Well I Took The Valve Covers Off And Didtn See Anything Aout Of Place, And The Noise Gets Greater When I Accelerate!!!!!!!! What Could That Be??? I Apreciate Any Help Guys!!!

 

Rod bearing. And I am willing to put my money it will be either cylinder 8 or 4. Those seem to be the 2 cylinders that spin bearings most of the times in these motors.

Could also be a main bearing.