| Re: The theory of the thermostat...
This is a complicated question and depends on few factors. first you need to think of the temp range you want it to operate in versus the temp range it was designed to operate in. most gm emissions controlled vehicles (cat, smog pump, egr, etc...) come factory w/ a 195 deg t-stat. If all other factors are correct, (water pump working, fan clutch working, rad of proper capacity, no leaks) then this normally yields a norm operating temp of 195-215. this is fine for normal use b/c it gets the cat to the right temp to do it's job. the ignition timing is also a factor, as normally the spark occurs later than it should for optimal performance, to compensate for high temps and reduce the risk of detonation.
I've found that running a 180 deg t-stat is optimal because- A: the carb/injection setup sees that the engine is up to temp and will not try to richen the mixture for a cold engine, and- B: you can run a more advanced timing curve w/o the risk of detonation.
in conclusion, pressure test your system for leaks, make sure your fan clutch/electric fan is working, (and this also means that it's not coming on too late.) water pump shaft spins freely, make sure you are using the proper rad for your engine size. get a 180 degree t-stat and check the timing w/ a light. also don't rule out the fact that the trans may be slipping, or that the engine simply could be overworked.
i hope this helps. sorry for the longwinded response, but just trying to cover everything i can think of. keep us posted. | 
