It's nothing but simple machining and an ability to use a micrometer and a calculator. Right now I'm in the process of installing a 235 rotating assembly into a 216 with all the modifications hidden so the engine looks like a bone-stock 216. The next couple of projects will be the "235" with 270 CID, and an "almost 300" 261. All of them will use original equipment type flat top pistons, and they'll have compression ratios of 9:1 or more.
The only reason to use a higher static compression ratio would be to compensate for a stupidly radical camshaft that doesn't close the intake valve until the piston is way up the compression stroke, requiring the remaining cylinder volume to be squeezed tightly enough to get back to the original compression pressure. Using popup pistons with a mild camshaft gets into cylinder pressures that limit the timing advance to a tiny amount to avoid preignition and detonation. One of my customers learned that the hard way when he insisted that I install 12:1 compression pistons in a Morgan +4 (Triumph TR-4 engine) without using a radical cam. Detonation melted the pistons. "There's no free lunch!"
Jerry
