Are there any GM Techs out there?

[Billy Nees]

Alright, I am pretty sure that I've got it. With the thermostat closed, coolant goes through the heater core and into the rear of the block and is circulated through the block and head by the water pump. When the thermostat opens, water goes into the LOWER radiator hose AND through the block and head. It goes through the radiator and into the UPPER radiator hose where it is circulated through the block and head until the thermostat closes . Clear as mud....