Ori if you have the piston in front of you, you might measure the diameter and depth of the trough as close as you can cuz it sure ain't gonna be a perfect geometric figure. if you get a cubic inches number (length x width x depth) then multiply that by 16.387064 to get CC's. EDIT How about this! Ori fill the trough with clay (dead even level) then take the clay out (all of it) & have your burette filled to maybe 50 CC dead even on the 50 CC mark then drop the clay in & see how far the water level rises. (knead the clay into a thin rope so it dont catch on the sides of the burette). MORE EDIT forget the burette, take the clay out & knead it into a perfect square then measure the sides (l/w/h) & do the math. MORE EDIT roll it into a ball in the palms of your hands cuz that will be way easier than molding it into a square then put the math on that, volume = 4/3 x (Pi x radius cubed) & the radius will be 1/2 of the balls' diameter then convert that cubic inch number you get into CC's. MORE EDIT Hey Dog, John is a post ho & he would not pass up an opportunity to kick his numbers' higher & he does know the 383 piston ins/outs