How do you run a overhead on 427 mack engine?

To run an overhead adjustment on a 427 Mack engine, first, ensure the engine is at operating temperature and turned off. Then, remove the valve cover to access the rocker arms and pushrods. Use a feeler gauge to check the clearance between the rocker arm and the valve stem, and adjust the set screws accordingly to achieve the specified clearance, typically around 0.020 inches for intake and 0.025 inches for exhaust valves. Finally, reassemble the components and double-check the adjustments before starting the engine.