This is how I checked chamber voulme of my head of the GT40P. I had them shaved .030".
I got a piece of plexiglass which you can get at Home Depot for $12 for 18"x24". Make sure you get the .220"(1/4") thickness. The .093" is too thin.
Now you need some white lithium grease that you can get at any parts store.
Your going to need something to measure the volume of the chamber. Now I tried everywhere and the easiest was going to a drug store and getting an oral syringe for infants. I picked this up for $3.25. It is in the incriments of 1 mL which is the same as 1cc. It goes up to 10mL.
Now you have to place the head on some kind of stand or table that is fairly level. I positioned the head at an angle for air to reach the top so it doesnt get stuck at the bottom.
Next I cut the plexiglass with my sawzall about the size of the combustion chamber. Drill a 5/8" hole near the top where you will be filling it and so air can escape.
Now you have to put the plexiglass on the head and seal it and this is where the grease comes in to seal the glass against the head.
Now is the time where you fill the chamber with water. Make sure you insert a spark plug!! Now fill the syringe with water up to 10mL.
Now keep repeating this and count how many times you put it in. When it gets close to full start putting in smaller incriments and add them up and you got your chamber volume. I would do it twice to avoid errors and to double check your work.
This cost me a total of $18 and roughly and hour to do it
