Attributes . Approximate compression ratio for 1968-72 and 1977-82 302 CID is 9.49:1 with 54.5cc heads. Approximate compression ratio for 1977-82 302 CID is 8.97:1 with 54.5cc heads. Approximate compression ratio for 289 CID is 9.12:1 with 54.5cc heads. . Names