[Shotimes] there arose such a clatter

[van Oss]

When my 91's engine (142K) gets hot from in-town driving, on launches I hear
valve clatter.  (I know that sound, trust me.)  The SHO's radiator is new,
system has been flushed several times.  A few questions:

--- I want to be clear about treating the main issue vs. treating the
symptom.  Talk to me about that.

--- If this is a sign of engine wear, what parts?  How serious?  Any
work-arounds?

--- Is clatter a sign of dirty valves?  If so, is Motorvac a solution?  If
not, what else?

--- Alan Fanning or others, where can I get a 195F thermostat?

--- I'm about a millimeter from deciding to install a manual switch to turn
on the radiator fan.  Anybody got wiring advice?  It's a good time to tackle
this, since this car will soon get an engine-start switch, gauges, and other
electrical mods.

Joseph van Oss