There is no problem with the lifters...or oil supply to the top end. A tiny bit of oil is metered by the lifter [ different brands use different results, but result is the same ] with each cam rotation. Eventually it fills up the prod...bit by bit....to lube the top end.
If there was no restriction by way of the metering valve, you would have 16 oil geysers....& no oil pressure at the bearings.
