piston to wall measurement

first the wrist pin is offset in the piston /and how you use the piston determines wall clearance keith blacks have a special dome with a accumulator groove on the top to hold the heat in so you run tighter clearances less ring wear .stock .0015/.002. stockcar 2/barrel .0025 /.0035.4barrel .004/.005 on the bottle.006/.007.also a different ring gap for all types of racing.