Don't know if this applies, but I had same issue on my '89 Probe, it too is 3 valves per cyl with SOHC :
Problem there was the tiny little holes in the rocker arms that supply oil to the hydraulic lifters can easily get clogged up, resulting in valve clatter, however this clatter does not go away.
Solution : remove the lifter train and rod out each lifter passage with a thin wire ( I used piano wire of the correct size ).
Worked fine on the Probe, no more lifter clatter .........
BTW, it had 106,000 miles on it .