Yes. In CA. the road draft tubes were eliminated in 1961. I'm not talking bronze carmel color, I'm talking thick black sludge. After the switch to 190 degree thermostats, the engines looked cleaner and yes when pulling heads the bores were in much better shape. IMO the later introduction of unleaded fuel and common fuel injection also did wonders to improve engine cleanliness and engine wear in typical driving scenarios.
The high temp thermostats were used to help prevent condensate on manifold surfaces and bores on the carbureted engines. The goal was to improve air-fuel mixing. This allowed a leaner idle and cruise mixture because of better cylinder to cylinder mixture distribution. The engines did not have 3 way cat converters and often ran leaner than stoichiometric at light throttle cruise (for emission purposes).
Now with port injection, some engines are going back to a lower thermostat opening for a little more power. The port injection has excellent fuel distribution and mixing, the cat handles much of the emission work, and the lower temp cylinder walls and manifold increase charge density slighly and reduce detonation. Bore wash is no longer a big problem since the demise of the frequently horrible automatic choke.
I'm not a one size fits all advocate here. For many people doing typical short trips with numerous shutdowns in cool or cold conditions the high temperature thermostats have been in the plus column.
[ August 21, 2004, 11:07 AM: Message edited by: tpi ]
