In case Dave or someone else reading this wonders, engine build specs (and maintenance specs) are for ambient temps of about 68°F (20°F) since that is about a reasonable target for measurement.
Obviously tolerances change (tighten up) at operating temperatures, but it would be much harder to regularly measure components at operating temperatures (harder to handle and impossible to keep them at a steady temp).
So specifications are based on components at a common ambient temperature.
Valves set to that clearance cold will tighten up hot, but not enough to hold a valve open which would prevent it from cooling and eventually destroy it.
Hope that logic helps.
