Your cam card lists lobe lift, or valve lift at a specific rocker ratio. This shows the lift your valves will actually see with the rockers you're running, and what other ratios would give you.
| Rocker ratio | Net valve lift |
|---|
The rocker arm is a lever. A 1.5:1 rocker moves the valve 1.5 times as far as the pushrod moves it. Solid-lifter cams run with lash (a small gap), which the valvetrain has to take up before the valve starts to move, so it comes off the total. Hydraulic lifters run without lash.
Cam cards often list "valve lift" already multiplied by a stock ratio, typically 1.5 for a small-block Chevy or 1.7 for many Fords and LS engines. Divide that number by the listed ratio to get lobe lift, then use the ratio you're really running.