I followed your instructions. The steam valve starts admitting air very early, somewhere around 45 degrees before TDC. It can be tweaked a little with the front adjustments, but nothing close to that much. I wonder if the eccentric might be off. Those four page instructions talk a bit about the eccentric, but (to me at least) they seem backward (contrary to what I'm seeing and the overall drawing on the plans).I have never set up a Corliss, but how hard can it be ?
My guess is as follows:
1. Figure out if you are trying to set the valves with the engine running over, as in the video above, and make sure you are not setting the valves for running under, which would have the flywheel rotate backwards from the video.
2. Remove the cylinder head from the end of the engine, and with a little air pressure turned on and fed into the top of the cylinder (using the normal feed point like in the video), rotate the flywheel to top dead center.
The upper valve near the cylinder head that you removed should start to admit steam either just before the piston reaches top dead center, at TDC, or slightly after TDC. If you don't hear air coming into the cylinder somewhere around TDC, adjust the gear so that that event happens (called setting the admission point).
3. Rotating the engine to bottom dead center (BDC), as you rotate towards bottom dead center, the upper valve near the flywheel should start to open somewhere just before, at, or just after BDC. Perhaps you can feel a pull on the flywheel when that valve begins to open.
4. A lower valve should start to open when the piston is about 70% down the stroke (check me on that) to release the cylinder pressure.
5. The upper valves can trip shut anywhere from 12% of stroke to some late amount of stroke, depending on how much cutoff you want.
I don't think the cutoff point is critical for an engine with no load, but when running on air, you may want a little later cutoff since air does not expand like steam.
Does this make sense?