What is the Combustion chamber of this heads?

An easy way to CC heads is to get a piece of plexiglass that will cover the combustion chamber. Drill a small hole at the top edge of plexiglass and combustion chamber. Take a thin layer of grease and put in around the chamber and put the plexiglass on....you might need to secure it with some tape. Then a a syringe with CC increments on it and fill it with some type of cooking oil and start filling the chamber up......keep track of the CC's of fluid you put in and you'll know the chamber size close enough for your calculations......I always do a couple of chambers and get an average.