'71 Dart 6.4L swap progress being made!

GoldSwinger71 said
WORD OF CAUTION - If you are using the Classic Auto Air (or any system that uses an electronic blocking valve to the heater core rather than a blend door) - You will need to install additional T's on the coolant line to the heater core path for a return to the engine when the heater is off, otherwise you will only have coolant flowing on one side of the engine. Another shop buddy was working on an E body and wondering why only one side of the engine was heating up. The coolant had no return unless the heater was switched on.

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That could have been bad. At least the lesson was learned without destruction (and not on my car / engine.)

I'm having a hard time understanding this. I can't believe Chrysler designed an engine that uses heater hoses as a means to carry coolant to critical engine locations. Take a look at the water pump. The suction side of the pump goes to the center of the impeller, just like all water pumps. Water is then discharged directly into the block. The suction side of the heater hose is in a similar location (red circle on front).
Now to return side. The water comes out the head, returns to a small section of the block, then goes through the timing cover into the top portion of the water pump and thermostat housing. The heater hose connects to the block in this area. (blue circle)
The way I'm seeing it, you can plug both of the heater hose ports, which I'm sure some racers already do, and you won't have a coolant flow problem.

I also think someone commented about the pump blowing the lines off. Pressure in an automotive cooling system comes from the expansion of the coolant as the temperature increases, not from the water pump. If they are blowing lines, their hose clamp must have been loose, or they were using a radiator cap with too high of a pressure rating.

I could be completely wrong here, but someone needs to explain the science behind Chrysler using heater hoses for a main path of coolant.