What is the dumbest method for adjusting valves on a 6-cylinder engine?
2 Answers
Open the cylinder head cover and rotate the crankshaft to observe the movement of the 6-cylinder valves. When the intake and exhaust valves exhibit overlapping movement, it indicates the exhaust top dead center (TDC) of the 6th cylinder. At this point, the 1st cylinder is at the compression TDC, allowing adjustment of the 1st cylinder's intake and exhaust valves, the 2nd cylinder's intake valve, the 3rd cylinder's exhaust valve, and the 4th cylinder's intake valve. Then rotate the crankshaft 360 degrees, locate the compression TDC of the 6th cylinder using the same method, and adjust the remaining valves. In other words, based on the engine's firing order, after determining a cylinder's piston position at compression TDC, you can adjust the intake and exhaust valve clearances for that cylinder.
Back when I worked on old inline-six engines, I used the most rudimentary method—adjusting the valves without removing the camshaft. After shutting off the engine, I'd remove the valve cover, prepare a feeler gauge and wrench, then rotate the crankshaft in the firing order 1-5-3-6-2-4 to position each piston at top dead center. At this point, the corresponding valve rocker arms would be completely loose, allowing me to slide the feeler gauge between the rocker arm and valve stem. I'd then loosen the lock nut and adjust until the feeler gauge could just be pulled out with slight resistance. The whole process required two people—one to turn the crankshaft and another to adjust the clearance, relying on the audible 'click' to confirm proper adjustment. While this saved on specialized tools, it was easy to mess up the sequence, and I had to recalibrate three times before daring to start the engine.
