I took the heads off my old motor before I sent it in as a core, and the skirts were definitely not coated. I took 2 pistons out to free the motor up and make it turn before sending it in. There is an upgrade to a new type of chain tensioners, with some type of new design plastic or Teflon. It hopefully won't sit long enough to spit out a rocker arm, as is common in wore out motors. There's some kind of rocker arm fix on the market for 4.7 and 3.7, but I've wondered if it's a snake oil salesman!