If your're running the hi-perf roller lifters, you have a very narrow window
of lash adjustment for them to work correctly. If I remember correctly, the
block is grooved inside the cam bearing journals, so its highly unlikely a misinstalled cam bearing. There is a possibility that the oil galley plug on the front of the block
behind the timing chain may not have been staked in correctly and could've become dislodged. There are also some on the back of the block, but you would've noticed a leak similar to the worst rear main seal that you've ever seen.