Priming 340 engine and rocker arm oiling.

Newbomb Turk said

If you know the span between the holes in the block (or in the bearing) you can measure the span between the holes in the cam. IIRC I looked at that years ago and the time the holes in the block line up with the holes in the cam only for a few degrees. I mean where they are both totally open.

Im not sure but I have at least one other cam out in the shop. So I can compare at least two when my cam gets here. Should be Thursday.

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I think the amount of time the cam holes are aligned with the camshaft holes are what is relevant. Not when the camshaft holes are aligned with the block holes. Assuming the camshaft bearing and the block holes are aligned. If you increase the cam bearing hole diameter you increase duration or if you make the cam bearing hole into a slot in the direction of rotation you increase duration. All the while the block hole doesn't change.
I think ultimately what you want to measure is the amount oil that reaches the rockers. That's the job of that circuit.
I think you need to know pressure, time (duration) and the size of the smallest orifice in the flow path. There would other factors like viscosity and the turns and other obstacles in the flow path. Also keep in mind that oil starts flowing at the point when the holes begin to align through a tiny orifice. As the cam rotates the orifice size increases as the hole uncovers, fully lines up and then closes back up. A varible size orifice over time. To futher complicate things flow through the varible orifice will change with a change in pressure (rpm) and viscosity (temperature).
I think it would be difficult (impossible for me) to calculate the oil flow to the rockers. But, I'm not sure even if you could measure it what that would tell you.
At the risk of oversimplification In the end you need enough oil to lubricant the rockers/valve train. Not enough oil will be evident with worn or damaged rocker/valve train parts. Too much oil may rob needed oil from other parts in the engine (worst-case). Too much oil might just be inefficient and not damage anything else (better- case). But having the right amount not too much and not too little in other words most efficient is usually the goal in competitive racing (best- case).