A local guy near me had the same type of problem with water getting in; it only occured once the motor got warmed up real good. It was on a known/salvaged 427. It had a single cylinder on a block that was sleeved and he went through 4 seperate attempts on that block to fix it until they finally "pinned" the impacted cylinder somehow and resleeved it for a 4th time. Based on what I saw him go through, it would not seem prudent to put yours back together until you are absolutely sure what's cracked or if its worth saving; hopefully it can be fixed right the first time. Good Luck.
