I recently put a 180 thermostat on my '85 350 with a stock temp gauge. When I get on the freeway and the truck is in a constant acceleration, the temp needle will go all the way up to 260 then drops down to 180-190, and never goes above 210 after that. The funny thing is that there are no signs of over heating when I pull over after the temp needle has gone that high. Its like the engine HAS to get that hot for the thermostat to open for the first time. Its onle a one time thing for the day. 1. Is my truck really getting that hot, or is my gauge bad? 2. If it IS getting that hot, why? 3. If the gauge is bad, is there like a bad wire or something?