GC160 Won't Turn Over

Hello friends. So I'll start with a short backstory of this engine. I purchased a pressure washer with this Honda engine for $100 and it didn't run (knew that when I bought it). The problem was no compression, turns out the exhaust valve wasn't seating all the way for some reason so I used some sea foam and elbow grease to hopefully break loose the carbon deposits and restore compression, and it worked! but only for one season :-(. So then I purchased new valves and tore the engine down and replaced them. everything seemed to have gone fine but now the engine will not turn over. I have determined that it has something to do with the rod or rod cap. The piston moves freely in the cylinder and the crank rotates just fine. I tested the crank with the timing belt and cam shaft attached, so all of that is moving find as well. The valves are also moving as they should. As soon as I tighten the rod cap down, and I'm talking anything past hand tight on the bolts, everything seizes up. I did replace the rod cap, but not the whole rod, because I broke the oil dipper off the old rod cap accidentally. I've double and triple checked the torque on the cap bolts. Bought a new torque wrench to make sure I was within the calibrated range of the wrench. Even at 50 in-lb (torque spec is 108 in-lb/9 ft-lb), nothing moves. I'm completely at a loss with this thing.
 
I've looked through the service manual and nothing is sticking out at me. Anyone have ideas?