Question: with this hole/oil return in the front of the block, does it affect the oiling to the lifters
Answer: Oil comes up the shaft in the centre of your picture and flows forward through the "cast in" pipe in the block to the front of the valve chamber of the block. The A pump can provide good pressure (about 100 psi) and , because it is not capped, delivers a good volume of oil for lubrication and cooling purposes. I have read that it is about one gallon per minute.
The engine sits at about 3 degrees incline. Oil flows forward over the dam wall on to the timing gear and back along the valve chamber where it gravity feeds to mains and cam bearings with about 1 and 1/2 inches of oil in this "header tank" with about seven inches of head pressure to the main bearings (this equates to roughly 3 psi ).
The centre main feed oil tube can be seen just near valve 4 boss. Excess to needs oil flows back to the block via the external oil return tube.
FWIW...Very early blocks (about 1200 of them) had two cast in oil pipes emanating from the oil pump shaft but this was quickly discontinued. These 1927 blocks had no oil return pipe feed from the valve chamber cover back to the side of the block.
The oil supply dam located on the side of the block has good and bad points. The good side is that the engine has a reliable supply of oil available for the mains bearings on start up ":O).
The bad side is that you always have some dirty oil remaining when you change oil ":O
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