All head gaskets take a little "set" when they warm up, even the supposed "no-retorque" types. On something as easy to reach as a stovebolt engine, I choose to re-check the head bolt torque after the first warm-up, then tweak the valve adjustments if necessary. The valve cover has to come off anyway.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!