Put the pistons 1" down the bore. Wipe a little grease on the cylinder wall just above the piston and rotate the engine until the piston is only .500" from the deck surface. Make sure the grease is sealing around the crown of the piston. Get yourself a cc'ing plate and measure it. If the engine is still in the car, get a piece of plexiglass and make sure the hole is at the very top of the cylinder. Record your measurement. Now multiply: bore x bore x .500" x .7854 x 16.38. Now subtract your measured volume from the volume you just figured here and you'll have your dome volume. Obviously you can use any figure you like down the bore, I'm just using .500" for reference purposes.