The hydraulic lifters for the Magnum small blocks with the hollow pushrods, what in the lifter design determines how much oil is metered through the pushrod on every cycle of the lifter?

there's a very small oil metering hole in the cup on the lifter. That would be most of the cause. The rest of it would be determined by how much pressurized oil is forced into the lifter.

My magnum conversion engine certainly gets plenty of oil on the top end. Its a 77 360 block with a summit K6901 cam and Summit 7.650" chromemoly pushrods.

goldsuster318, you hit the topic I'm looking for. I'm trying to reduce the oil flow to the heads a little and am trying to find out what would be the best way. I wasn't looking for restriction in the pushrods as I'm a little fearful of pluggage. I just thought the lifter would be the best area to concentrate on.