Well then I guess all the hot rod mags and thousands of tech articles I've read over the years, not to mention the MANY blocks I've bored soniced and sleeved through the years are for squat. It's well documented the 340 and 71-73 360 blocks ARE thicker than any small block from 74-up. I've proven it on the boring bar. Let me give you this example and I'll leave it alone. I specifically remember sleeving a 340 block years ago. Depeding on who makes the sleeve, it can be pretty thick. The outside diameters are far from the same on all the different makes. Hell, two of the same part number can be different in O.D. by .060" or so. Typically, installing a sleeve requires boring a hole somewhere in the neighborhood of .100" - .150" over from wherever it is. This particular block I was REAL familiar with cause it was MINE outta my 1973 Rallye Charger. Yup, it was the numbers matchin 1973 date coded block. I ran it hot like an idiot when I was 17 and it overheated the small end of a connecting rod and a piston pin slid out and carved a notch in a cylinder wall. Snake Hogan was still teachin me the ins and outs of that Kwik Way borin bar so I got to do it myself. I remember takin over .125" outta that bore and just for kicks, the old man put the sonic checker on it. It still had almost .070" in the thinnest spot. He wasn't surprised though because he told me that the 340 was very thick because it was already basically .040" over from the start and they designed it and the early 360s the same way. That old dude knew his dookey when it came to machine work. He was a legend around here......especially with the Harley crowd. What I'm talking about has nothing to do with core shift, but with how those early small blocks were actually cast. If I'm not mistaken, those early LA 318s are the same way from like 67-73. That's why you can punch some of them out to a 4.00" bore and still have some left over. Lots of people have done that as well. Yeah, I agree 100% sonic checkin is a MUST, but I'm tellin you from first hand experience the early blocks are thicker.