Aside from a large camshaft, cubic inches, and lots of fuel, compression is the element that allows power to be formed. It’s the massive amount of squeeze being placed on the fuel and air, which in turn drives the piston down. However, in engine building, before determining the amount of pinch on the piston, the volume of its combustion chamber (measured in cubic centimeters) must be completed first. For the most part, measuring the volume of the combustion chamber on a cylinder head is a cinch and involves filling the chamber with a fluid (alcohol with food coloring) and taking note of the amount used. In addition, its methods can be carried over and used to determine the volumes of the intake or exhaust ports, too.
While cylinder head manufacturers advertise their combustion chamber volumes, some cylinder head castings can produce slight variances in chamber size. By taking the time to measure each chamber, it’ll ensure your engine will take full advantage of the combination you’ve put together. Moreover, establishing the cubic centimeters of the combustion chambers will dictate piston design (flat, dome, or dished) and will help determine the correct compression ratio, while the chamber volumes will also tell if the cylinder head will need to be milled in order to meet your specs.
To handle this month’s task, we headed over to Quarter Mile Performance in Chatsworth, California, where we began by disassembling our test subject, a pair of small-block AFR 225 cylinder heads.