Above: You will use outside micrometers for most measurements in your engine. Here, QMP’s Rob Bieschke is using a Mitutoyo 2- to 3-inch outside mic to measure main bearing and connecting rod journals of an LS7 engine he is assembling for a customer. Really high-end measuring instruments can read very precise values. The LS7’s rear-most main journal measures 2.55925 inches. That’s to the hundred-thousandths of an inch!