Since the motor has not been apart it is still running at high compression. From the factory it is 10:5 to 1. I'll bet that it is a little higher from carbon deposits. I use Shell 93 Octane and it does not ping. Everything is stock. I just started using Torco Octane Boost which claims 97 Octane at one mixture (I used this one and (I think) 105 Octane at a full mixture.
As I understand the Fel Pro gaskets that are on the market for the head gasket in this engine are much thicker and will reduce the compression level to 10 to 1. I do have three NOS GM head gaskets for this motor so I can keep it at the factory setting.
Marc
