Before building an engine, it's important to measure all the engine components to make sure they are within approved operational limits. Even new parts can sometimes sneak through factory quality control to actually end up in the marketplace out of specification. At MMS, "check, double check, and document what you've checked" is a standard operating procedure.
In this video, Paul explains the critical importance of measuring tolerances on the starter for the rear engine of the Cessna 337. Once completed this airplane will return north for continued missionary service in Canada.