If the coolant were ONLY circulating in the block, it would overheat and boil over in just a few minutes. Since you say it is NOT overheating, then the coolant has to be travelling through either the radiator or at least the heater core (but you say you are getting no heat). That says to me that there is no restriction to the flow making the coolant stay IN the block long enough to heat up. I'll bet the gas mileage sucks pretty bad, too, right?
