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A 400 block is standard at 4.32. It is not a warrenty block, no way would they go to the trouble to sleave it back to 4.31. A sonic check would tell how thick the walls are. My guess is its a industrial block(they are the best blocks for strength) that started out at 4.25 bore and can go to 4.375 like the 400.



A 400 block is standard at 4.342 , that's nice and thick where it is , but if he wants to bore it out it would be best to have it sonic checked , I had a 230 block that needs 2 sleeves because of core shift to go out to 4.375


Sorry for the mistake on bore size,thinking one thing typed another.