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Typically...how much under standard bore sizes is a KB hyper piston typically? I know you have to measure the actual pistons used, but do they usually run .0015 or ? under the std bore sizes?(Std, +.030, +,.040, +.060, etc).

Is there a rule of thumb?



They are tight because the pistons dont grow much. But the clearance is determined by bore diameter and intended performance. But still its a very tight perimeter.

.0015 to .0055 from small bore NA to large bore supercharged.

The clearance is measured at the skirt parallel to the balance pad height.

Whats even more important IMO, is the top ring gap. As it is closer to the top of the piston vs other type pistons that it requires extra top ring gap to prevent butting of the ends.

Example, NA 4.36 bore race gasoline motor = .033 top ring gap.