I was running 15.5 in my 440 with Iron heads.It ran on 93 octane.I really couldnt hammer it on the street as it would have clatter but for just driving it was OK.I do have a big cam at .588.With the aluminum heads its much better.I do have to agree anout 10 to 1 is about all you want in a mild build.My kids 62 300 413 runs about that and it never clatters.Rocky