Cam/Head Swap Disaster.......

Well, I as far as I can see I took all the correct avenues while disassembling and reassembling the engine after I wiped a lobe on the previous cam.

I swapped in a used set of late 70’s 360 1.88/1.60 heads with new seals, springs and retainers and lapped the valves. Went to break it in 20 minutes ago and started spraying milky fluid out of the oil filter or should I say through the rubber o ring. I stopped it immediately and I’m now faced with a perplexing situation. What would cause water to leak into the engine before it’s even started? And what would cause so much pressure that it pushes by the oil filter seal??

I had filled the radiator up last night and it wasn’t until all this happened did I realize when I went to open the cap today that it was empty. I filled it up not thinking that it could have been an issue. The only things I replaced were the heads, cam and head gaskets. I used a set of NOS .024 head gasket lightly sprayed with copper seal. I’m bumming hard on this and really have no clue where to look. Any info would be greatly appreciated.

Thanks,
Jake