Loud “Pop” after priming oil pump
..............and inspected the push rods.....
Location, location, location......
Did you happen to notice or hear the area of where the pop sounded?
I had a stuck relief valve on a SB oil pump causing zero pressure that released as soon as I broke one pump mounting bolt loose. It made a pretty good hollow sounding pop. I knew right away where it came from. No way I was using that pump again.
Other than that, IMO, it's pretty easy to "miss" the rocker cup when bolting down rocker shafts if you're not continually checking them during tightening. This "could" cause a pop as it springs into the cup if one wasn't in and the valve seats. I'd go through them again at least tension, TDC for each pair. Spin 'em to see if one may have bent.
If your fuel pump misses the pump rod I'd think a pop might be possible.