25 years ago, I had an a-hole (Bill Richardson at RAM) talk me into partially filling a mint 1966 Street Hemi block with hard-block. It was an important part of his machining package. Got the engine back, and within a few weeks it developed a horizontal crack about 6" long in the block, following right along the top edge of the hard-block. Since then, I've been a non-hard-block guy. As for the Hemi, at almost the same time, it has the #1/2 rod journal swallow a glob of orange silicone that a-hole had let float loose, so the custom $2500 Crower lightweight crank and two of the custom 7.400" Crower lightweight rods were scalded along with the block.