I drove my 351 Cleveland for 4 years under the hood of my 72 Gran Torino Sport running nothing but regular. Now that you mention it, I believe it did only have 9 to 1 compression and it does have open chamber heads. I'm getting it rebuilt right now so I'll have to have a talk with the speed shop owner.
Closed chamber heads are the ticket for power and efficiency. The open chamber heads came along later because emissions regulations, not because they improved anything. The fact that they run hotter to burn cleaner is the exact reason they detonate. Closed chambers run cooler, therefore are not prone to detonation. They run "dirty" though, when it comes to emissions.
