Cylinder Head Bolt

Many are stretch bolts designed for one use. They are tightened in a set sequence and in stages. Torque and angle values come from the manufacturer. Threads in the block must be clean and, where specified, lightly oiled so the torque reading is accurate. Aluminium heads often require final angle tightening rather than a simple torque value. Some engines require retightening after a running period, but many modern gaskets do not.

Correct clamping force keeps the gasket sealed under combustion pressure.

Reusing stretch bolts can cause gasket failure. Wrong sequence can warp the head.