After 65+ years of tinkering with worn out engines of all sorts, I've come to the conclusion that there's only one surefire way to clean up a water jacket- - - -strip the thing down to the bare block and use a rotary table hot water jet washer with a strong cleaning solution to flush all the crud out of the cooling system passages, the crankcase, the oil galleries, etc. I just bought one of those jet washers- - - -which will arrive sometime later today or tomorrow. A good condition used one can be purchased for $6,000.00 or so, which is why most hobbyists, and very few commercial shops don't have one. A new one will cost about $8K-12K or so.
www.ebay.com/itm/336264730196?Jerry
