[cdan34]

Ken, my v12 is being worked on right now and I've been thinking about how to relieve the crankcase pressure. I don't know if that is your problem. But I did have this with my last flathead v8. What I did is, create a vacuum from the exhaust with check valve pulling through a small oil separator. This takes pressure from pan and valve lifter area. I think that relieved the pressure and when I unscrew the separator I find mostly water with a slight bit of oil.
I might do this with the v12 when I start putting it together.

Good luck

Chuck