The attached link (here) provides some discussion on a loss-of-power incident (no one hurt, but damage to the aircraft on landing). The engine builder had apparently installed the rocker arms in such a way that the adjusters needed to be backed out >far< too much. (Maybe the pushrods were cut too short, or too many shims under the rocker arm supports). As a result, the hole in the adjusters that allows oil to pass from the rocker arms to the bearing was not in position and instead may have been entirely outside the rocker arm. This had two results: -- No lubrication to the bearing that rides on top of the valve stem. It was frozen on the affected engine -- The valve adjuster was weaker due to the drilled hole being outside the rocker. (See above. Only a tiny bit of the valve adjuster is visible above the lock nut on all of the cylinders. Not right). As a result, the adjuster broke and the engine suffered from reduced power. There are very good instructions, photos, and videos of how to build these engines, but it's important to pay attention to the details when doing the work. The NTSB report noted that there were burrs on the crossdrilled hole where the adjuster failed, and that this might have increased the likelihood of a stress fracture there. Does anybody here routinely de-burr these holes? I guess it wouldn't hurt anything, but it would seem unnecessary if the adjusters are correctly installed (since that portion of the adjuster shaft should be well inside the rocker arm and not be under appreciable stress).