How to Adjust Valves on an 8-Cylinder Engine?
2 Answers
8-cylinder engine valve clearance adjustment is performed according to the firing order of 1-5-4-2-6-3-7-8. Valves are responsible for introducing air into the engine and expelling exhaust gases after combustion. Structurally, they are divided into intake valves and exhaust valves. Below are the specific adjustment steps: 1. First, bring cylinder 1 to top dead center (TDC), then adjust the intake and exhaust valves of cylinder 1, the exhaust valves of cylinders 5, 4, and 2, leave cylinder 6 unchanged, and adjust the intake valves of cylinders 3, 7, and 8. 2. Next, rotate the crankshaft 360 degrees to bring cylinder 6 to top dead center, then adjust the intake and exhaust valves of cylinder 6, the exhaust valves of cylinders 3, 7, and 8, leave cylinder 1 unchanged, and adjust the intake valves of cylinders 5, 4, and 2.
Adjusting the valves on an 8-cylinder engine requires careful attention, and I’ll share from experience. The engine must be completely cooled; otherwise, the valves expand due to heat, leading to inaccurate clearance measurements. Prepare the tools: feeler gauge, wrench, and manual—the manual contains the standard clearance values, typically 0.008 to 0.012 inches. Follow the firing order, such as 1-8-4-3-6-5-7-2, and address each cylinder in sequence. First, rotate the crankshaft to position the cylinder in the compression stroke, with the piston at top dead center and the valves closed. Then, use the feeler gauge to measure the clearance—gently insert it until you feel slight resistance and stop. Too little clearance can cause valve burning, while too much creates noise. Loosen the nut and adjust the screw to the correct point, then tighten it. After adjusting all eight cylinders, start the car and listen for smooth operation. Performing this regularly extends engine life and prevents knocking or power loss. Remember, safety first—wear gloves to avoid burns or oil stains.
