After completing a head, cam, lifters, pushrods, and timing chain replacement I attempted to prime my oil pump with a strange results. Since the oil fill is on the drivers side I left the passenger side valve cover off so I could watch when oil began to flow from the pushrods while using a priming tool. After approximately 5 minutes of priming I was unable to see any oil flowing from the pushrods on the passenger side head. Just out of curiosity I removed the drivers side valve cover and had plenty of oil on the rocker arms and in the head area, so I spun the priming tool again and observed normal results as oil flowed from all 8 pushrods and over their respective rocker arms. Having performed oil pump priming many times in the past this was the first time I have ever seen oil reach one head and not the other. Has anyone else seen this happen when completing a rebuild? Should I consider the engine properly primed and ready to run? What, if anything, would cause oil to reach only one side of the valve train and not the other? I know some of you are engine builders extraordinaire, and would love to either find out this is okay, or what steps I need to take prior to engine start. It doesn't seem normal to me, but I cannot figure out what would prevent oil from reaching the passenger side pushrods, and only the passenger side pushrods. The valves were adjusted prior to installation of the intake so I know all the pushrods are properly seated in their respective lifters. Also, every component is brand new, pushrods, lifters, heads, rocker arms, etc. No oil is seeping from anywhere on the engine during the priming process. I have seen the most unusual engine issues this year in two consecutive engine builds. Global warming? Trump's fault? Russian interference? My newfound senility?