i measured a set of arias pistons i just bought. there is a .044 inch (little more than 1mm) taper from the piston skirts to the crown of the piston.... that is.. there is a 20 thousandth of an inch piston to wall clearance on either side of the piston at the very top. the skirts are perfect (.004 total clearance.) does this seem excessive to anybody?? these measurements are accurate within .001 inch


[Modified by supergreenSol, 5:56 AM 3/23/2002]

 

yes it should because with the heat from the combustion chamber it will cause the piston to expand and fill in the gap

 

usually when measuring pistons, you want to measure in about 2 places on the piston that is perpendicular to the piston pin bore. 1: just below the piston crown(below ringland) and 2: tip of skirt. you never wanna measure accross the the ringland because it can be anywhere from .020"+ smaller than the tip of the skirt measurement.

 

Not to mention too that pistons aren't designed to be perfectly round... Always measure at the skirt below the oil control rings, perpendicular to the piston pin bore, just like SuperGreen Sol said.