Stuart!
"
The only reason a modern automotive system runs at 212° is because it was designed in Detroit to run at 212°." .... and the small block was designed to run above 180!!
a thermostat is to get the engine up to a
minimum operating temp as fast as possible and make sure it doesn't fall below that, nothing else
see here - if Detroit designed the engine to run at 212, it won't matter what thermostat you put in, it'll run about 212 once warmed up,
and water would start circulating at the 'stats rating regardless if it were 160 or 180, 175 or 200
the cooling system ain't rocket science - running an engine too cool results in poor fuel use, acid buildups in the oil, and excessive wear - running an engine too hot results in the rad boiling over - the reason rad caps have increased in pressure ratings over the years is to allow the engine to run at a higher [designed] temp without boiling over, and the reason the 6's used a zero to 7# cap and the sbc uses a 7-15# cap is the sb runs at higher temps, altho both might have the same rated 'stat .... and I've never heard of a 200° thermostat in a small block, but they run at that temp all day long
the answer to waggy's original question is, it's better to use a 180° 'stat on a 350, and if the cooling system is in good condition, with a 12-15# cap, a 'normal' operating temp of about 200 is not a problem .... and will not be related to the 'stat temp .... but check the actual water temp to see if the gauge is accurate
