So you're saying the -7 on the end of the casting number in this picture means the cores were replaced 7 times. Interesting. I hadn't heard that before. Thanks!
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Yes, at least I was told/read that many years ago... Rule of thumb was to look for a block with a low dash number. Yes, a sonic check is the true test. I used to get asked to sonic check, and now that I got one, not asked once, lol....