Well I ran a quick pressure test on my (freeze cracked) 455 Olds block. It seems to hold pressure (about 10 psi of air) in the water system without much pressure loss that I could tell. So that should mean that the crack is not too bad, and it doesnt seem to be leaking into the oil galley anywhere. So I guess I will JB the external cracks and get this boat on the water. Hopefully my pressure bypass valve will cure the high pressure aspect.
There is some residual milkshake oil. What is best to clean this up, ideally without pulling the intake? I think someone said kerosene but how much is too much? Do you run the engine with kerosene in it or just pull the valvecovers and dump it all over? I did a search but could only find milkshake prevention threads, not how to actually clean the milkshake out... but I could be search-handicapped.