the idea that a 180 thermostat should keep the engine at 180 is wrong ... the thermostat simply controls the minimum temp for water circulation to prevent an engine running too cold - it doesn't open until the water is 180, then the water can move thru the rad and get cooled - if the engine tends to run cooler or the cooling system is overkill, then the water is cooled faster than the engine heats it and the thermostat may start to close again - under those conditions the temp will hover around 180, but small blocks "like" to run hotter ... what regulates the maximum temp of the engine is the design of the engine, my 235's have consistently run cool, needing a 180 thermostat to keep the temp up, my 283 consistently runs hotter, regardless if the thermostat is a 160 or 180
aren't pressure caps used to allow water heating above what would be boiling at atmospheric pressure? if simply putting a lower rated thermostat in made the engine run cooler, why have a pressure cap?
Bill