Priming 340 engine and rocker arm oiling.

Good question. I don't know how you would measure it.

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.