propeller feathering while ground run

[cessnadriver]

Hello ALL.
So to begin. I purchased a field overhauled front engine, IO360C, and replaced the baffling to install it into the rear position. So after installing the engine I was trying to get the fuel system adjusted. I found that during run-up, about ten minutes, the propeller went to feather! I checked the prop rigging and replaced the prop governor. Call a local prop shop, East Coast Prop, Lancaster, Pa. The tech told me it sounded as though the governor was not getting enough oil? The oil pressure was only 30 PSI. And that the latching pin maybe be the problem, but he didn't think so?? The engine had only run for about 1.5 hours since overhaul, I checked the oil condition, which was black as coal? I drained the oil and replaced the filter. Cut the filter open and found some fine grit. I'm thinking that the the case was NOT cleaned properly before reassembling. So I contacted TCM and asked their Tech about the problem. He told me that the "Transfer bearing" maybe clogged or maybe not installed correctly? The bearing hole not aligned with the crankshaft? I also did the pressure check of the prop governor ports. Suppose to be 20-50 PSI, mine was just at 20 PSI, minimum pressure! I removed the pan, thinking it was full of contaminates? Some grit/sludge was in the bottom. While the pan was removed I found a chunk of gasket or solid sludge in the pickup oil screen! Removed the chunk, run the engine---SAME FEATHERING problem? Any thoughts???
Thanks as always!
Regards, BILLS