ASE A1 Engine RepairCylinder Head and Valve TrainHard
A technician is performing a multi-angle valve job on a cylinder head. After cutting the 30-degree and 45-degree angles on the valve seat, the technician observes that the contact area (seat width) on the valve face is too wide and is too close to the margin of the valve. What corrective action should the technician take?
- AUse a wider 15-degree top cut to lower the seat.
- BUse a wider 60-degree bottom cut to raise the seat.
- CDecrease the depth of the 30-degree angle cut.
- DIncrease the depth of the 45-degree angle cut.
Show answer & explanationAnswer & explanation
Correct answer: A. Use a wider 15-degree top cut to lower the seat.
If the seat width is too wide and too high on the valve face (close to the margin), the 15-degree top cut needs to be widened (or deepened) to lower the effective seating surface and narrow the seat width.
Why the other options are wrong
- B. Using a wider 60-degree bottom cut would raise the seat contact area even further on the valve face, exacerbating the problem of it being too close to the margin.
- C. Decreasing the depth of the 30-degree cut would make the 30-degree cut less effective, potentially making the seat wider or not moving it correctly.
- D. Increasing the depth of the 45-degree cut would primarily deepen the seat, potentially making the seat wider, not narrower, and not necessarily moving it away from the margin.
Multi-Angle Valve Seat Adjustment
The process of using multiple cutting angles (e.g., 15°, 30°, 45°, 60°) to achieve optimal valve seat width and position on the valve face for proper sealing and airflow.
- 45-degree is the primary sealing angle.
- 15-degree (top) controls seat position and width.
- 60-degree (bottom) controls seat position and width.
- Proper width (0.040-0.060 inches) is critical.
Memory trick: Too wide and high, cut the top to fly.