Hi volume oil pump vs standard volume pump

I can relate to clearance issues, but I put the engine together myself and checked all the bearing clearances. They were all within factory spec.
I'd more inclined to point at the lifters as the problem area at the moment.

During prelubing with the intake off, I noticed some tiny bubbles forming at a few lifters.
This could be from the fact that either the lifters' oilbands are located fairly high, and/or the LA360's lifter bores have a deep camfer at the top.
I can see this bleeding off quite some pressure when the oil gets warm and thinner.

I hope to solve this by installing a HV pump and hopefully be able to go down in oil weight again a step.