Combustion Chamber Volume
To properly calculate the compression ratio of an engine, you need to know the combustion chamber volume. This can be called "CCing" the chamber. In other words, measuring the combustion chamber volume in cubic centimeters. Since I had large valves put in my cylinder head, I was pretty sure that the volume would have changed somewhat. Also, during the porting process, I did some unshrouding of the valves and polishing of the chambers. The polishing was done to reduce the size of any lumps or other irregularities. Think of these as a cooling fin with a temperature gradient down it. Just like the spark plug, the tip of the lump will be hotter than the base since it is further from the cooling source (cooling water.) This hotter spot can lead to pre-ignition (detonation) which can be destructive and will limit the amount of boost that can be run. In any case, I had done a little work polishing and grinding the chamber which changes the volume and compression ratio.
You seal off the individual chamber using a very thin layer of vaseline. Then you fill the graduated cylinder and note its volume. I just filled it to the 100cc mark. You slowly add the fluid and fill the chamber. When its full, you note the level left in the graduated cylinder, and the difference is the volume of the chamber. All four of mine worked out to 60cc +/- .5cc.
A couple of hints. Tilt the cylinder head slightly by shimming one edge. Also, locate the fill hole at the top edge of the
combustion chamber. This allows the bubbles to move toward the hole, and you can completely fill the chamber. That's all there is to it.