Motor to Cold?

You sort of have a catch-22 situation with motor coolant temperature. Most of the power in gasoline goes right out the tailpipe and cooling system in the form of heat. If you could design an engine to run at much higher temperatures without melting parts, it would be more powerful and more efficient. On the other hand, cooler intake air is denser, and so it makes more power. That being said, I think 180* is the best compromise, and what you should shoot for if possible. Blocking off the exhaust crossover in the intake manifold will keep the manifold much cooler, but there is a price to pay in the winter as the intake will be slower to warm up, and the fuel will not atomize as well. Aluminum intakes do much better in this regard because aluminum conducts and dissipates heat much better than cast iron. As far as tolerances go, yes the coolant temps will affect how much the block expands, but how much does maybe 20* really make? I'm not sure. The pistons are still exposed to the same combustion heat no matter what your coolant temps are, so I would imagine they expand as they should. How cool is too cool. Probably anything under 160* Getting back to Aluminum. My engine routinely ran 200*, and would run as high as 230* in stop and go traffic. Then I put in the Griffin Aluminum radiator and a 160 stat, and the engine never went over 185* no matter what. It would run at 170* most times. That was with iron heads/intake. Then I went to the TA aluminum heads and Edelbrock Performer intake. Picked the car up at Stage1 Performance in February. The outside temps were about 40*, and the engine coolant temp would not go over 140-145*. Thought my Autometer gauge was broken. I finally had to go to a 180 stat. Now my temps are 178-180 at normal speeds. If I get stuck in traffic on a hot day, I see 185-190* tops. I noticed a definite increase in power with the higher coolant temps. I think the aluminum heads like it when you keep more heat in them. Just my experience.