Just as a comparison, my 400 is a street only engine with TH400 and both a 3.25 and 3.89 rear gear sets. I have the Isky 234/242 duration with .520/.540 lift on 110 lobe separation. It has just enough lope to really sound good. This engine was built as a mild street, stop light to stop light engine. My best friend drag races a 400SBC (drag race only) and runs a cam in the 260/270 duration range and 106 separation. The roundy round guys run mid 240's/250's on 108-110 separation in 350's that just don't have the low end torque the 400 has. Maybe some of the 400SBC engine builders will add their two cents worth also. Keep in mind that valve lash drops that total lift figure down some, the 400 stroke can handle smaller lobe separation than 350's, and lower compression engines with long duration cams can benefit from advancing the cam. iF YOU GO FLAT TAPPET, CAM BREAK IN IS A PAIN. I LIKE ROLLER CAMS