The head is currently off my engine. There is also no radiator or water pump on the car. I was thinking while the head is off I could clean out the water passages on the engine block. Is this worth doing and if so what should I do? I've read somewhere that hot water/vinegar might help clean this out. Of course I'd have to be careful to not get water in the oil passages or cylinders. Maybe fill, let sit overnight and flush out next day.

hose it out thru the water pump hole. mask off the top of the block to keep water out of the oil passages. I just used a garden hose. I had big chunks of green goop in my cooling system.