I have an 84' Jetta w/ 1.7L EN engine

I heard an extremely light valve tapping noise about a year ago and over
time it is getting slightly louder, I want to check the valve shims
clearance. IIRC, My Haynes manual says to check these when at engine
operating temperature. That's kind of hot to be working on the engine.
My mom's Haynes for her chev. pryzm says to check when cold. What does
the Bentley say about checking them? and what specs are given?

Thanks in advance.