pre-lube a new engine
 

Hello, I am new to TruckForums and hope that my question is appropriate to this section. To start, I have a remanufactured chevy V-6 long block (vin Z) installed into a 1988 c1500 1/2 ton chevy. This is bolted to the OEM 5-speed manual tranny, and I also reused the original oil filter adapter, oil cooler lines and (professionally cleaned) radiator. All other parts are new or came new with the long block, including a new oil pump. My problem (and question) is that I am unable to pre-lube the engine. I am using a distributor shaft, minus the cam driven gear, to spin the oil pump shaft manually. Yet, I am unable to get oil to the upper engine components, specifically the push rods and rocker arms. In fact, after approximately 5 rotations of the shaft, I reach a point where it takes a good deal of effort (torque) to rotate it further, as if pressure has built up against an amount of resistance. I have taken apart the filter adapter, oil cooler lines, and filter to inspect them and all looks fine. What am I overlooking? Thanks for your help and suggestions.