Cylinder compression is 120 to 150. That's not good. Quite a range there. I agree with Ian and Dave's assessment regarding a blown head gasket. You didn't state if the engine had been overheated previously. With a leaking rad, water pump etc, it probably did. A small pinhole in the head gasket will pressurize the cooling system and show up as lower compression. The gasket probably failed in more than one area allowing coolant to travel to an oil drain gallery. Not sure if you were actually able to pressurize the internals of the block to 2500 psi as stated while you were washing the guts but if you got it anywhere over max rating (guessing 50 psi), your gaskets including the intake wouldn't have been able to handle it. That's the only way for coolant to get into the oil (unless something cracked). Is there coolant back in the oil now?

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