I don't use the measurements from my dial calipers or inside mikes as the gospel, I measure the inside mike I.D.(length) with my outside mikes and record the length and then measure the crankshaft journal or whatever I'm trying to find the clearance on with the outside mike and due the math for the actual clearances. If your going to check cam lift and degree the cam in you will also need a one inch travel dial indicator and mag. base dial indicator holder as well as a degree wheel marked in one degree increments for the full 360 degrees of the wheel, the larger wheels are easier to use and read. There are a lot of machinest tools that are nice to have but not absolutely got to have tools to do the basic checks on engiine clearances.