I ran 91 octane, 9:1. 489 CI. 8pds boost, non intercooled, Steel heads, 30 Degrees adv and all was ok. AT THE LIMIT THOUGH.... I WOULD NOT DO IT AGAIN! I bumped the timing to 34 Deg. Smoked 4 pistons in 15 seconds. I will now run 91 octane, 8 pds with a static compression ratio of 8:1, aluminum heads with 30 degrees of advance. BDS has a chart on their website that computes these limits for you. http://www.blowerdriveservice.com/techcharts.php