Adjust valves on inline gm 6?

To adjust the valves on an inline GM 6 engine, first ensure the engine is at TDC (top dead center) on the compression stroke for the cylinder you're adjusting. Use a feeler gauge to measure the clearance between the rocker arm and the valve stem, typically around 0.020 inches for intake and 0.030 inches for exhaust, depending on the specific engine model. Loosen the locknut on the rocker arm, adjust the screw to the desired clearance, and then retighten the locknut while holding the screw in place. Repeat this process for each cylinder as necessary.