Is it better to tighten Headbolts with Hot Engine

Or does it not make a difference if engine is cold? Thanks Stan

torque them down when it is dead cold.

Definitely torque while cold. This is how engines are assembled initially, and that's what the specs are made for. Stuff is different sizes when warm. If you torque while hot, you're liable to have things either loosen up as the engine heat cycles through use, or to simply break something.

Same thing applies when checking oil levels, and tire pressure, always check when cold.