What effect does the tightening sequence of the Cylinder Head Bolt have on the engine?

1. Ensure sealing
The tightening sequence of the Cylinder Head Bolt is directly related to the sealing between the cylinder head and the cylinder block. Since the contact surface between the cylinder head and the cylinder block is uneven and there are tiny gaps, these gaps need to be compressed by the pre-tightening force of the cylinder head bolts to achieve the sealing effect. If the tightening sequence is improper, the pre-tightening force in some areas may be too large or too small, affecting the sealing effect, and then causing the leakage of coolant or oil.

2. Reduce stress concentration
A reasonable tightening sequence can disperse the pre-tightening force of the bolts and reduce stress concentration. If all bolts are tightened to the maximum torque at one time, or the tightening sequence is unreasonable, it may cause excessive stress around some bolts or bolt holes, causing fatigue damage to the material, and even causing serious consequences such as bolt breakage or cylinder head deformation.

3. Improve assembly accuracy
Gradually tightening the Cylinder Head Bolt in the prescribed tightening sequence can ensure the assembly accuracy of the cylinder head and the cylinder block. This is because, in the process of gradual tightening, the preload of the bolt can be continuously adjusted to make it more evenly distributed, thereby ensuring that the key assembly parameters such as the flatness and parallelism of the cylinder head meet the design requirements.

4. Extending the life of the engine
A reasonable tightening sequence can also extend the service life of the engine. Since the tightening state of the Cylinder Head Bolt directly affects the sealing of the cylinder head and the stress of the cylinder body, the correct tightening sequence can ensure that the engine maintains stable performance during long-term operation and reduce failures and damage caused by problems such as poor sealing or stress concentration.

5. Improving engine performance
The tightening sequence of the Cylinder Head Bolt is also closely related to the performance of the engine. If the tightening sequence is improper, it may lead to poor sealing between the cylinder head and the cylinder body, which in turn affects the combustion process in the cylinder. This may lead to adverse consequences such as reduced engine power, increased fuel consumption, and worsened emissions. Therefore, the correct tightening sequence is crucial to improving the performance of the engine.