I have seen as much as .002" without issue. Rule of thumb is 80% of the diameter should be within tolerance. The more times you cut caps and line hone, the lesser of the full diameter can be restored at the parting line. Some racing blocks may be line honed 8-10 times after multiple bearing failures. They can be a challenge. Worked with a student last night on a Toyota Supra in-line 6. 7 fairly large main housing bores. 1000 HP engine. Really tough to get all 7 right on the money. The factory didn't even try. They supplied 8 different main bearing sizes, each .0002" different. This engine had 5 different sizes in the same engine. Once rebuilt, all the bearings are the same size. Tough job. Hard to believe a stock bottom end can take 30+ lbs. of boost.
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