From Red Hamilton:
If you graph the valve events in relation to TDC and each other,
you can see that TDC is not a very good guide for setting valve
lash. The Ford/Motors Manual method works, barely, for stock cams;
it does not work well with hot rod cams.
A recipe that works for all engines and cams is:
Set the intake lash when the exhaust valve on the same cylinder is just opening and the exhaust when the intake valve on the same cylinder is just closing.
For those who have trouble remembering the intake opening, exhaust closing method, just get the valve opened to maximum lift, and then rotate the crankshaft exactly one turn. The lifter for that valve is now on the heel of the cam.