I have the 103 engine, and always run premium, or av gas. Looking at buying some heads, question is what comp ratio should I try to get. I was thinking 10:1. But local indy says that will just cause me pinging and other issues. He thinks 9.3 would be better. Basically keep my stock piston, and add heads. To get 10:1 I'd have to add a new pop up piston as well as the heads.