The Fault - Valve spring installed at an angle
An uneven valve spring assembly causes unequal compression, leading to bending when the valve opens due to camshaft movement.
The valve fractures at the lowest groove
The fracture starts at the top of the third groove and runs across the valve shaft.
Pressure marks can be seen in the cylinder head
There are uneven pressure marks on the contact surfaces of the valve spring in the cylinder head.
This leads to a broken valve
The fracture surface exhibits the typical structure of a forced rupture.