did your motor(s) fail, or did you just decide to rebuild??
my buddy just redid both of his blower motors, and while testing he decided to have Nickerson look at his plugs for him under the microscope. Dean told him that there was water coming from somewhere on the one side of the motor. So we pulled the one side and didn't see anything obvious until we pressure tested them and found the crack. Who knows how long it's been cracked???