RE: saito 91 intake push rod doesn't move.
Jeff,
A cam lobe can wear-away if it was galled by the cam-follower, as a result of improper machining, or tempering.
It can also happen if incorrect cam timing assembly was performed and the cam was forced to turn over, with a valve pressing against the piston...
Once galling has begun, the cam-lobe will keep wearing away...
A cam-lobe cannot become completely flat, while the engine is running, because with zero lift, the engine cannot run (obviously)...
With the lift diminishing as the lobe wears away, power will reduce until the engine cannot even keep idling...
Even then there will still be some lift...
As the un-experienced user keeps on grinding the engine with the starter, hoping for it to eventually start, the wear goes on until lift is zero...
If your engine ran well before it became a 'hangar queen'... it is more likely that the cam-follower is somehow stuck...
But that would hold the valve in an open position... Unless, that is, you re-adjusted the valve-lash...
I don't think there is enough room to cater for a complete loss of lift...
...I have a bachelor's degree... not a doctorate...