Valve torn off suddenly? In most cases, this is due to incorrect assembly rather than defective material! Even the slightest carelessness often leads to serious problems in the workshop. Today, Louis will help you to avoid mistakes when installing valve springs in the future, making sure that your customers don’t show up again at the workshop a short time later—with damage that might be even more serious than before the “repair.”
Out of line: incorrectly installed valve springs lead to valves tearing off!
If you carry out repairs on the valve train incorrectly, a valve may break off during operation under unfavorable conditions.
This is generally caused by a valve spring installed at an angle: the most common assembly error in this type of work. If you assemble the valve spring canted—and don’t notice it—uneven forces act on it, because even when the valve is closed, the spring is more compressed on one side. When the valve now opens, the spring is pressed onto the block. The stroke of the camshaft creates a massive bending moment in the upper area of the valve shaft. Starting from the lowest groove on the valve shaft, this can cause the valve to be torn off. It can then fall into the combustion chamber, become trapped between the piston and cylinder head, and be severely deformed as a result.
An overview of the typical damage characteristics:
- The damage occurs immediately after the repair.
- The fracture starts at the top of the third groove and runs across the valve shaft (see Figure 1)
- Valve keys are partially deformed at the partitions.
- There are uneven pressure marks on the contact surfaces of the valve spring in the cylinder head (see Figure 2).
- The fracture surface exhibits the typical structure of a forced rupture (see Figure 3).
You must bear this in mind during every installation!
When mounting the valve springs, ensure they are seated correctly in the cylinder head. And when installing new valves, always replace the valve keys!
