How to adjust the valve clearance of SFH C9 engine?
3 Answers
There are two common methods for checking and adjusting valve clearance: the cylinder-by-cylinder adjustment method and the two-step adjustment method. Below are the steps for checking valve clearance: 1. Remove the valve cover: Unscrew the fixing bolts of the valve cover, carefully remove the valve cover, and take care not to damage the valve cover gasket. Wipe off any oil stains on the valves and rocker arm shaft with a cloth to facilitate the valve adjustment process. 2. Rotate the crankshaft: Ensure that the intake and exhaust valves of the cylinder being checked are fully closed, and the tappet must be positioned on the base circle of the cam. 3. Measure the valve clearance: Insert a feeler gauge of the appropriate specification between the valve stem and the rocker arm (or cam). Gently pull the feeler gauge; if there is slight resistance, it indicates the clearance is correct.
I have plenty of experience adjusting valve clearance. For the SAIC Hongyan C9 engine, it's best to operate when the engine is cold. First, remove the valve cover and rotate the crankshaft to position cylinder 1 at top dead center of compression. Then use a feeler gauge to measure the clearance between the valve stem and rocker arm. Typically, the intake valve clearance is 0.25-0.35mm, and the exhaust valve is around 0.35-0.45mm, but you should always refer to the manual for exact specifications. If the clearance is incorrect, first loosen the lock nut on the adjustment screw, turn the screw with a wrench, then tighten the nut after adjustment. Remember to adjust other cylinders sequentially according to the firing order 1-3-4-2. Before reinstalling the cover, clean the sealing surface thoroughly. This operation requires precision, as improper adjustment can affect power and fuel consumption.
Last time I adjusted my friend's C9 engine, I made sure to have all the necessary tools: feeler gauge, wrench, and torque wrench. The first step is to turn off the engine and wait for it to cool down completely, otherwise the measurements won't be accurate. Locate the crankshaft positioning pin hole and align the marks, then adjust the first cylinder to top dead center before measuring the clearance. It's important to note that the exhaust valves are prone to carbon buildup, so if the clearance is too large, it should be adjusted promptly to avoid a clicking noise. After adjusting each cylinder, rotate the crankshaft two full turns to check. Finally, use the torque wrench to tighten to the specified torque—never rely on feel, or you might end up with loose screws causing trouble while driving.
