ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is performing a valve job on a cylinder head. After grinding the valve seats and valves, the technician measures the installed height of the valve springs. The specification for installed height is 1.700 inches ± 0.015 inches. The technician measures a spring installed height of 1.730 inches. What corrective action should the technician take?
- AProceed with assembly as the measurement is within specification.
- BInstall shims under the valve spring to decrease installed height.
- CInstall shims under the valve spring to increase installed height.
- DReplace the valve spring with a new one.
Show answer & explanationAnswer & explanation
Correct answer: B. Install shims under the valve spring to decrease installed height.
The measured installed height (1.730 inches) is above the maximum allowed (1.700 + 0.015 = 1.715 inches). To bring the height within specification, shims must be installed under the spring to decrease the installed height.
Why the other options are wrong
- A. The measurement of 1.730 inches is outside the specified range of 1.685 to 1.715 inches (1.700 - 0.015 = 1.685; 1.700 + 0.015 = 1.715).
- C. Installing shims under the valve spring would further increase the installed height, moving it further out of specification.
- D. Replacing the spring might be necessary if it's fatigued, but shimming is the primary method to correct installed height if the spring itself is good.
Valve Spring Installed Height
The distance from the spring seat to the bottom of the retainer with the valve closed, critical for proper valve spring pressure and preventing valve float.
- Affects valve spring pressure.
- Too tall (low pressure) can cause valve float.
- Too short (high pressure) can cause premature wear.
- Adjusted with shims under the spring.
Memory trick: High spring, low pressure; add a shim to trim.