ASE A1 Engine RepairCylinder Head and Valve TrainMedium
A technician is performing a cylinder head overhaul and needs to verify the installed height of the valve springs. The service manual specifies an installed height of 1.850 inches with a tolerance of ±0.015 inches. The technician measures a spring at 1.870 inches. What action should the technician take?
- AAdd a valve spring shim to increase the installed height.
- BAdd a valve spring shim to decrease the installed height.
- CReplace the valve spring with a new one.
- DInstall the spring as is, as it is within tolerance.
Show answer & explanationAnswer & explanation
Correct answer: B. Add a valve spring shim to decrease the installed height.
The specified installed height is 1.850 inches ± 0.015 inches, meaning the acceptable range is 1.835 inches to 1.865 inches. The measured height of 1.870 inches is above this range. To decrease the installed height, a valve spring shim (which sits under the spring) should be added. This effectively raises the spring seat, compressing the spring more and reducing its installed height.
Why the other options are wrong
- A. Adding a shim decreases, not increases, installed height.
- C. Replacing the spring is unnecessary if the height can be corrected with shims; the spring itself may be perfectly fine.
- D. 1.870 inches is outside the acceptable range (1.850 + 0.015 = 1.865 inches).
Valve Spring Installed Height
The measurement of a valve spring's length from the valve spring seat to the underside of the retainer when the valve is fully closed, critical for maintaining correct spring pressure.
- Affects valve spring pressure and potential for valve float.
- Adjusted using valve spring shims.
- Too high: low pressure, valve float; Too low: high pressure, premature wear.
Memory trick: Height too high? Shim it low, spring pressure flow.