I have a timing light but it does not have a set back dial. My dampner does not have a degree scale on it..just the tdc mark. I thought this cacluator was interesting and might be helpful if you measure your dampner and plug the information into this calculator. The other article also helped me...
I got this from the Corky Bell, "Maximum Boost" book.
This is for gasoline.
The lowest value is .052 hp x cid x absolute pressure (boost + 14.7)
The highest value is .077 hp x cid x absolute pressure
Corky stated that this is from a compliation of years of dyno tests.