Sealing that valley plate mounting hole with RTV did nothing.
So, I pulled the intake manifold and that 3/4" dia hole does go to the water jacket. It is drilled pretty deep before hitting water.
Just the very bottom of it was not covered by my intake gasket. Just a sliver shooting water out.
I called Koffel's place and they said that hole is not there from the factory. Surprise, the guy I bought these heads from must have drilled it to modify the water cooling pattern.

I will just plug them and put it back together.