Lash setting features for castellation mechanism

An engine brake rocker arm assembly for a valvetrain and operable in an engine drive mode and an engine braking mode, the engine brake rocker arm assembly configured to selectively open one of first and second exhaust valves in the engine braking mode and comprising:

• a brake rocker arm configured to rotate about a rocker shaft;
• an engine brake capsule assembly movable between (i) a locked position configured to perform an engine braking operation, and (ii) an unlocked position that does not perform the engine braking operation;
• an actuator assembly configured to selectively move the engine brake capsule assembly between the first and second positions;
• and
• a lash setting tool configured to removably engage the engine brake capsule assembly and move the engine brake capsule to the locked position to enable mechanical lash adjustment while the brake rocker arm is assembled in a valvetrain and the engine brake capsule is assembled in the brake rocker arm.