Which end does the Heater hose plug into the Heater control valve on a '56 CDV

[Wacco65]

Which end does the Heater hose plug into the Heater control valve on a 1956 Cadillac Coupe deville?

[J. Gomez]

Which end does the Heater hose plug into the Heater control valve on a 1956 Cadillac Coupe deville?

From the Service Manual Section 16 Fig 16-B-1, from the water pump to the lower end of the heater valve the top end goes to the “T” to both LH and RH heater cores.

Reversing these may cause the valve to open from the pump pressure causing water to flow to the heater cores. 

Good luck..!