My 250 used to do that, it would climb right up the gauge, open, then cool off and run just fine from there on out. I believe I cured mine by moving the temp sender probe to a port right under the thermostat. It was mounted in the head between #1 and #2 cylinders. I suspect the water gets much hotter there, fooling us into believing the engine is overheating. The probe gets a much more even temperature where it is now. The 250 and 292 heads are the same, and I have heard the 292's run a bit hotter in the cylinders.
Joe
