Very high time O-320 with fretting when the crank case halves join by the main bearings. Note the reddish deposits inside the case indicating auto fuel use. Rechecking the thru bolt torque might have prevented this.
"I needed a very high quality print to enter in a photography art show. I had my photograph printed at a superb printer, using a very expensive machine. I also ordered the same print through Photobucket. And yours was superior!"