If you are going to put heater bungs in the water tubes, you may as well put an electronic heater control valve in the pressure side heater hose and remove the OEM heater control valve. You should pass track-tech with this arrangement too because if the valve is closed, the heater core and hoses in the passenger compartment are not under pressure. There used to be a kit available that would allow an electric heater control valve to be controlled by the OEM lever. I haven’t seen it lately but it wouldn’t be too difficult to come up with your own solution. If I recall, Roland (@LeMans850i) did this recently.
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