The Moroso was about 4 months old by the time the engine was assembled & running. Antifreeze was added due to the alloy heads & the chorinated tap water was harsh on everything alloy. It was noted that there was a soup in the radiator a few weeks after the run in period, so everything got flushed. Since there wasn't a cooling problem after, it never got looked at again & the engine got used. Because it had an overflow bottle & a suck back radiator cap the overflow bottle was the reference & it never looked bad. The fresh soup had jammed the rad cap up so the flow was blocked both directions. Months pass & there's the odd high temp noted on the guage but it cooled down. Eventually it turned to a horror story, the engine running like a steam train, the engine got pulled. this mud like soup was everywhere. after the big strip & clean we found the Block fill was all gone????? this was the soup & the cooling system was only filled with water & antifreeze. I think the electrolosis of the antifreeze reacted with the block fill & just ate at it till it was all gone. i dont know if soaking it would do it. i think it would need circulation.