Head Bolts Replacement Advice
THE REASON FOR REPLACEMENT THEM
- Stretch Bolts are used in aluminium Cylinder Heads and always need to be replaced after use.
- The aluminium Cylinder Head will expand up to 4 times more than the older cast iron Cylinder Head. This is due to the high thermo conductive materials used within modern engines.
- The Stretch Bolt is designed to work with the aluminium Cylinder Head unlike the older (re-usable) Bolts.
- After use, Stretch Bolts are weakened and are not strong enough to be used again.
- Please see the diagrams to identifying what happens when Stretch Bolts are re-used.
1 Stretch Bolt before installation.
2 Threads have become weakened after re-use.
3 Shaft has become weakened after re-use.
THE REMOVAL
When removing, it is essential to follow the sequence and use the correct tool stated by the engine manufacturer in relation to the Bolt head.
THE INSTALLATION
- Ensure the Bolt holes in the Cylinder Block are clear of contamination.
- Bolts are no longer torqued to a pre-set load, a standard torque wrench is only used during pre-loading.
- Use a degree gauge while torqueing.
- After this the Bolts are tightened via degrees of rotation and will not be affected by the friction during loading.
