For instance, a typical small-block Chevy like the much-maligned 305 has a stock rocker arm ratio of 1.5:1. A cam lobe with 0.3 inches of lift multiplied by 1.5 equals a valve lift of 0.45 inches.

We used a set of Trick Flow 1.6:1 roller rocker arms, which increased the cam’s advertised lift (calculated with 1.5 rockers) from 0.550 inch to 0.586 inch.