timing and octane relationship

With iron heads, I found that my car could take 13* on 87. I know some can't even run 8* on 87. It really depends on application. There is no linear relationship between base timing and octane ratings. I'd knock it back to 10*, and if it doesn't ping, sneak up on it 1* at a time until it does detonate. When you find where it does start to detonate (audibly), knock 2* out of it, and leave it alone.

For example, if you start to hear detonation at 14*, knock the timing back to 12*.

Joe