None of the early engines need much flow or pressure as they don't have highly loaded bearings or bushings or need oil to help cool the engine.
The 4 cylinder engines have a solid part of the rod cap that passes through the trough to produce an oil mist that lubricates cylinder walls, wrist pins, rings and rod bearings, etc. The oil flow just fills the troughs and reservoirs that gravity feed oil to the main bearings. The valve train is lubricated manually by oil can.
In the early 6s rod dippers produce a little flow to the rod bearings but more important is the mist to lube pistons, rings etc. A little pressure is needed to lube the valve train.
99.44 % of the advise you get on oil pressure is from people with experience with more modern higher horsepower engines. Producing higher oil flow and pressure takes horsepower from engines that don't have excessive amounts.
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