This can't be good?

[36tudordeluxe]

Drained the radiator a couple of weeks ago and refilled with new coolant today and am now leaking fluid out of left side header flange. In my 221 had a erosion problem with the heads and was concerned may have happened in my 276 but when I removed thermostat housing and ran scope into head didn't see an an accumulation of crud as I did on the the 221. The engine never leaked water previously. Could head be leaking into one of my exhaust seats?