I am in the process of rebuilding a EM1. Previous owner had it almost completely disassembled to turn into a race car. I believe he plugged the coolant return from the heater core. Can anyone verify this plug does not belong here? I couldn't find a good pic online, and don't know anyone who has a b16a2. I checked diagrams and believe I should have a Joint, Tube 19500-PE0-000 in its place. I appreciate it!

 

After approval thread bump.

 

Yes, you are correct. That is actually a "rocker arm rail plug and washer" inserted into the threaded hole where the heater circuit port normally exits the cylinder head. Removing it and replacing it with the hose barb part number that you stated above (I didn't check it, so I am assuming you are correct) should provide the path necessary to re connect the heater core at the firewall. Also, you will need to check the thermostat housing for the other hose barb so that you can complete this circuit.

 

Awesome, thanks for confirming!!