A few observations:
1. Generally speaking a hotter motor produces less engine wear.
Engine wear at 160 is MUCH greater than at 210. In my view a H20 temp of 185 is a good compromise between wear and HP. One reason (there are others as well) that today's cars run at 210 is that it leads to longer engine life and less wear. A car consistently run at 160 will have as much wear at 25K miles as a 210 car does at 100K. Obviously if a car overheats, the parts will expand too much and the result is metal to metal contact, but the above statement is generally true, a motor running at 210 will have significantly less wear.
2. Generally speaking a cooler inlet charge creates more HP.
People believe that a 160 Thermostat will increase their HP because it is cooler thus leading to a cooler and by extension denser intake charge. This may or may not be true, see #3.
3. Generally speaking a warm engine atomizes fuel better than a cold engine. In a truly cold engine, fuel can drop out of suspension and puddle. This leads to either an overly rich mixture as you try to compensate for the fuel puddling, and poor atomization of the fuel that does enter the motor. This would explain flyfish picking up a couple of hundredths after a few runs, the fuel is atomizing better.
In the end what you want is a motor that is fully warmed up so that the fuel is able to atomize. You also want all the parts fully expanded to reduce abnormal wear. At the same time you the incoming air as cool as possible. Underhood air is frequently very warm and thus less dense.
In my view a 185 thermostat is a good compromise between being cool and engine wear. At the same time fabricating a cool air kit is well worth the time and effort.
Regards,
Joe Dokes
