I have a knock in the left rear side of the engine. I checked the valves, push rods, lifters, pulled the oil pan no noticeable damage to piston rods, crank shaft, or anything else. Checked the side clearance on the connecting rods, within limits. Engine has about 140,000 miles on it. Not sure what the next step is other than rebuild the engine. Had the heads redone about a year and a half ago! Thanks for your help!!