Okay, here's the story up 'til now. I have a 1977 FJ40 with the original 2F engine. I had an engine knock that I was trying to chase down. I started by disconnecting the plug wires one at a time to see if the knock could be isolated to one cylinder. There was no discernable difference. After that I borrowed a stethoscope and found the knock to be loudest at the timing cover. After finally getting all the tools I needed, I got the timing cover off, only to find no obvious signs of damage. The only thing I saw was some marks on the crankshaft timing gear that looks like someone whacked it a few times to get it seated properly. (see photo) So what's my next course of action. Do I drop the oil pan and see what there is to see from underneath? Do I bolt it back together and take it to a mechanic? I'm coming to the limits of my skills. Any suggestions?