You can run a 11:1 iron headed engine just fine on pump gas. Its the dynamic compression (DCR) you need to keep down around 8.25:1 or so in order to run fine w iron heads on pump gas. A little more on aluminum heads because of the aluminum dispersing the heat better. Check out one of the many DCR compression calculators and punch in your static compression #s as well as the intake closing before ABCD #s and go from there. Cam duration will bleed off excess cylinder pressure. With a little research, figuring, tuning, and the rite cam alot is possible. Buddy has an 11.2:1 340 W ported X heads. MP .509 cam and it runs fine on 91 octane. The intake closes 74 degrees before ABCD putting the dynamic comp. @ 8.15:1 cylinder pressure is 162. Runs awesome