Stop in for a cup of coffee

Just stopping by.
Found this while changing putting the carb back on last week.
upload_2022-6-28_9-3-5.png

No obvious trail from hoses, the t-stsat housing or the HDCTO. 2 and 4 spark plugs look the same as 1357 so don't think its head or intake gasket - fingers crossed. Bolt may into coolant passage; not sure.