-one thing they need to do is sonic test the bores up and down the bores right under each of the 5 head bolt holes per bore----because there is 5 vertical grooves up and down the bores inside the water jackets.
-those grooves are actually the thinnest segments of the bore walls----and they tend crack vertically when high cylinder pressures happen against the bore walls.
-I measured a lot of 400's years ago and found some of these notches to be as thin as .101" to .129"----BUT good notches should average around .186" thick----and good bore walls should average out at about .238" thick.
-I also found that cylinder #6 was always the thinnest and #5 cylinder was the next thinnest.
-400 blocks with casting #330817 have the thinnest walls and are only about .189" average thickness.
-the thickest bore walls I ever found were on the early 1969 to 1972 four bolt main blocks---but those blocks were always weak in the main webs and needed splayed main caps and then fill the empty main bolt holes with some sort of special threaded fastener and use loctite to lock it in there.
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-here's link back to a discussion a few years ago that might be of interest.
http://www.speedtalk.com/forum/viewt...e953f6d3e44f9b
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-sonic testing a stock SBC 400 for a 600HP application is a very tedious job and really should have a map made of each cylinder.
-I seriously doubt that you'd get more than 4--maybe even 8 numbers per bore-----but really that's not enough----it takes way more time to get the entire picture than most people would ever spend.