10.5 to 1 compression was advertised as Ultra-High-Compression!
Type -- Ultra-High-Compression V-8
Horsepower -- 345 @ 4600
R.P.M.Torque -- 440 lb.-ft. @ 2800
R.P.M.Displacement -- 394 cubic inches
Bore -- 4 1/8"Stroke -- 3 11/16"
Compression Ratio -- 10.5 to 1
Sorry about the poor resolution of the photo.
http://mywebpages.comcast.net/oldsfan/MySite/62starfire.html