Hard to start, rough running, loss of power and engine dies while turning

What led you to thinking the valves needed to be adjusted, and describe the procedure you used.

I'm surprised to see such a detailed set of directions. These should be a standard GM cylinder head with a common and simple procedure.

What works the best is to remove the valve cover from the first head, fashion a drain shield from a piece of cardboard so the spraying oil runs back into the head, then adjust the valves with the engine running.

Start with the first adjustment nut and back it off slowly. You'll hear the lifter clatter for a few seconds until it slowly pumps back up. Keep slowly backing the nut off until the clattering doesn't go away. Tighten it just enough for the clattering to stop. That's the starting point. Now tighten that nut one quarter turn. You'll get a noticeable misfire for perhaps as much as five seconds until that lifter bleeds down. Tighten the nut another quarter turn and do the same thing. Keep track of how far you're adjusting that nut. After about two complete revolutions, maybe three, the misfire won't go away because the lifter is fully-collapsed and that valve is being held open. Back the nut off just to the point where the misfire clears up. That's the second reference point. Now back the nut off exactly half as much as you turned it down from the starting point. If you went a total of three turns, back it off one and a half turns. That will put that lifter exactly in the middle of its range. There will be plenty of self-adjustment range now that the lifter can bleed down of the push rod gets hot and expands, and it can pump up when parts are cold and shrunk.

Do that for each valve, then do all of them on the other side, and you're done.