The cylinder head is not from this cylinder, I could not find the original Athena racing 47.6, so I made a compression ratio of 12.3 for 95 gasoline with my own hands, at the same time, the Athena manual recommends a degree of 13.9 for gasoline with an octane rating of at least 96, but the fact is that where I live there is no such gasoline, there is a maximum of 95.