its the cam...seen compression like that many times. there isn't enough swept vol. for a 3.90 stroke to have those duration numbers unless he has a 48-52cc chamber. When I ran that cam with a 3.90 stroke I had 58cc heads and ran 110 Torco. Happens when you choose way too big of a cam. The combo here would probably run ok on 86 octane an 40 degrees of timing. What cylinder head cc are we looking at here? If its in the 70's you need some thing with 258-264 @ .050 intake to get going...especially with a 4.10 gear and big tires.