In all the books i have here at my house all of them give a compression ratio of 9.3 for all 289 2V motors 65 to 68. But my 68 motor has 63cc chambers and the 65 to 67 heads have 54cc chambers. What am i missing here? I calculate 63cc to be 8.4. My question is do you think the books are wrong? Does anyone know what the ratio should be for a 68 2v 289 should be?