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Q: Engine rebuilding what's the deal with over sized parts?

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I was wondering what and why there are over sized parts for engine rebuild kits why do or would I need the larger parts? Looking to have my 91 civic si rebuilt and there are oversized and standard parts .

When rebuilding a motor there may be times that the crankshaft surfaces need to be machined due to damage or the piston bores need to be re bored to a larger size or the connecting rods are going on a crankshaft that has been machined. The use of over sized pistons, rings for a bored out block. Bearings are over sized when crankshafts are resurfaced. When resurfaced or bored out blocks the machining is a 10 thousandths of an inch of metal take off and the over sized parts will state how much they are over sized from standard.

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