It's not uncommon to find a "sand hole" in a cylinder casting that will open up when a large oversize piston is used. A bit of contamination during the casting procedure might go unnoticed for years until it's exposed during a rebore job.

We used to have problems with 350 Chevy race blocks with "core shift" problems. Standard-bore blocks would perform well, but when we bored them .030" over to make 355 NASCAR engines and then beaned 'em up to 600+ HP, it was possible to get a crack in a cylinder wall.
Jerry

Last edited by Hotrod Lincoln; 03/03/2014 5:11 PM.
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