If you have 12:1 compression in that motor, it will NOT, repeat, NOT run on any gasoline currently available without preigniting like crazy, even if you run premium gas. You have 2 choices here. You can either lower the compression ratio like Tom said, or add a water injection system, but even with water injection you would probably have to use premium gas to keep the knock under control. You can check out water/alcohol injection systems at
http://www.coolingmist.com. I used one on a street motor that had 11:1 compression and it eliminated the preignition (knock) really well, but I still had to run 92 octane to keep the engine happy.
