11 to 1 on pump gas

10.5.1 is about pushing it with iron heads & pump gas, that extra .5 point won't yield you any more power, but the chances of detination are going to be there, i'd shoot for 10.3-10.4 with good quench & call it good, it'll work on pump premium & you'll be able to put alittle timing to it, if you have to pull timing for .5 point your defeating the purpose & you won't be happy, my machinest stronger recammended i stay just below 10.5 on my 406 sbc or it WILL detinate, i trusted his word & i'm very happy, it runs on 91 with 36* timing, it also has a smaller cam, Dynamic #s are around 8.1, Static is 10.4x.