HV oil pump vs Stock oil pan
... the pump is capable of pumping more oil than the p/up can draw out of the pan...
Doesn't make sense - the oil will accelerate to satisfy the equilibrium conditions. Higher volume will mean the velocity of the oil in the pickup will increase. At the extreme, the concern would be that the drawing force of the pump would reduce pressure in the pickup until cavitation occurs. It would require the pulling pressure of the pump to exceed the vapor pressure of the base oil.
The math isn't hard to figure out. At 8gpm, or 1848 cubic inches per minute, and a 1/2" oil pickup diameter (~.2 sq inches), would create a flow velocity of 9240 in/m, or 770ft/m, or 12 ft/s (about 9mph). Hardly that fast. If a HV pump increases flow capacity by 25%, it's not going to suddenly strain an already unstrained system.
For reference, the pumps tested by engine masters on a 440 had a max volume flow rate (at max rpm) of 6gpm (4.9 for a stock pump). This would make velocities through the pickup about 9ft/s (7.3ft/s for stock). Notably, both the HV and the HP made the same max flow, and the same max pressure. Which means that both pumps had a 'high pressure' bypass spring, it's just that the HV model also has deeper rotors for reaching max pressure sooner - the HP and the STD idled at 32psi, while the HV idled at 49. Standard maxed out at 54psi, the HV and HP at 72-75. What was also notable, is that all pumps seemed to reach near their max pressure by 3k rpm (min rpm on their dyno). None of the power results suggested any measurable impact to HP. The total spread in measured HP was 5, with the HV making 1.1 hp more than stock and the HP making 3.1 more than stock. The Milodon super-high flow (6.6 gallons @ 80psi) made 538.1 hp - the only one to lose power vs stock.
As far as a pump 'emptying' a pan - at 6gpm, that's 24 quarts per minute, or 2.5 seconds per quart. How long does it take a quart to drain back to the pan? 2.5 seconds seems doable IMO, especially since the majority of oil flow is likely going through the crank and rod ends, and being flung right back into the sump area. With a nominal capacity of 5 quarts, having 1 quart return to the sump every 2.5 seconds seems fairly reasonable still.
Nothing in these numbers seems to make a HV pump a problem. None seem to indicate a stock pump is a good choice unless building a stock engine with stock expectations. A HP pump might work well with something that lives above 3k, but why give up the better idle/low-rev oil supply and faster pressure build-up at start-up?
