Well, I'm no Chevy expert, but as a general rule the clearances in an engine are designed for when it is hot. When the engine is cold, you get extra wear because there is less expansion and clearance. Somewhere I have an old engine manual that shows a graph for engine wear vs water temp. Wear dramtically decreased as temp increased, and conversely wear increased as temp decreased.
The breakover point was around 160 to 180 degrees. 180 and above had siginificantly less wear. 160 and below had significantly more wear. Thus as a general rule 180 degree thermostats should be the minimum you put in an engine.
It is possible to take operating temperature into account when rebuilding an engine. Most drag race only engines are designed for full clearances around 120 to 160 degrees (or sometimes less). This is because these engines never warm up, particularly those which shut down at the end of the run and are towed back. These engines thus have more clearance when cold. The problem is when they get hot - the clearances can be excessive.
Another problem is the complete removal of the thermostat. Ever seen an engine overheat because the water is too cold? I've seen this several times. The thermostat gets removed, and the water circulates too fast through the engine. The problem is that heat is not properly transferred from the metal to the water. As a result, some cylinders never get enough cooling and they run hot. I saw a 302 **** seize a piston and a 400 Chev gall a piston because of this. If the thermostat is removed it needs to be replaced by a disk with a fixed hole in the middle to slow down the water. (This is why people with cooling problems still scratch their heads when they take the thermostat out completely.)
