Reminds me of the time a buddy of mine had a nice 2nd gen Trans Am that his wife drove he came home one day and she told him the engine was making noise,he checks and sounds like a rod knocking,he decided it was a good reason to upgrade to a built 455 and proceeds to do so,while pulling the low mileage well built 400 he notices a big dent in the oil pan,his wife admitted she had run over something in the road and that was when the noise started.It was amazing the racket it made when after pulling the pan witness marks showed the rod was barely kissing the pan.James recently diagnosed a "stuck engine" that moved just a bit in each direction, turned out to be the crank hitting the oil pan just a tad. One bump with the oil pan removed and it rotated properly. You never know...