Using the cam lobe on the left side of this illustration titled "Starting on base circle of lobe", separate the lobe into 4 sections, North, South, East and West, just as if you were looking at a map. Using a micrometer or dial caliper, measure the North/South dimension. Write it down. Measure the East/West dimension. Write it under your North/South dimension. Subtract. Multiply the result times the rocker arm ratio (1.72) to find theoretical valve lift. Check the valve lift you just computed against the cam card or info on the box to see if they are close to the same.

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