engine bore is piston diameter or circumference

2009 BMW 323
25,000 MILES • 2.3L • 4 CYL • RWD • MANUAL
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ALILEO007
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hi sir my name is ali i am mailing you to ask small technical question i want to know that how engine bore is measured is it measured from one side of piston to another side of piston in straight which is called diameter or it is measured in circle which is called circumference of the piston that is outer side of circle well sir waiting for your humble reply thanks indeed
Jun 21, 2014 at 3:30 AM
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MHPAUTOS
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You measure across the bore of the cylinder, the piston is a little smaller in dia, also with a old engine measure in two positions down the bore, do not measure at the very top but below the lip on the bore to get a true size as the bore size will change due to wear.
Jun 21, 2014 at 9:25 PM
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