[GoreMaker]

I'm planning out the re-assembly of the coolant lines on my 77 Trans Am 400/4-spd with factory AC. My engine build has KRE D-port heads and I'm running hoses from the back of the heads to the water crossover at the front. The passenger side rear fitting is teed to connect a 5/8" hose that goes to the heater core, like the factory setup.

Based on what I'm seeing in the service manual, my car did not come with a vacuum-actuated cutoff valve for that line. There doesn't appear to be a provision in my climate controls for such a vacuum line so I'm inclined to think that's accurate.

My current setup in that area has no flow restriction going to the heater core, but I'm pretty sure the factory nipple that was pressed into the rear of the cast iron head had a built-in restrictor spring. Even the nipple that KRE provides for that location has zero flow restriction. It seems like my current setup would pull unrestricted hot coolant from the back of the right head and send it through the heater core and then into the suction side of the water pump, thereby pre-heating the cooled coolant from the radiator all the time. Should I be adding a flow restrictor to the line that goes to the heater core? What kind of flow rate should I be aiming for in that line?