I was just thinking, you might try just putting a copper washer on the stud that you installed in place of the lockwasher and see if this is your problem.

Where Are You From? Leavenworth, WA / Yuma, AZ

Do You own a car built by Durant? Several

I finally got a pic loaded. What I was referring to is the area under the water jacket, on the right side of the engine. The freeze crack will form on the underside of the water jacket. If it doesn't break out a chunk, it can be easily repaired with cooling system sealer.

Where Are You From? Texarkana, TX

Do You own a car built by Durant? Several plus 1