Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSLEXUS1998SC 300REPAIR AND DIAGNOSISENGINE PERFORMANCEENGINE CONTROLS - ADJUSTMENTSVALVE CLEARANCESELECTING SHIMS
1998 Lexus SC 300
Selecting Shims
1998 Lexus SC 300SECTION Selecting Shims
- Shims can be selected using 2 methods. One method is using a shim selection chart. If this method is preferred, go to next step. Other method is using a formula. If this method is preferred, go to step 3).
- Using micrometer, measure thickness of used shim (shim that was removed). Using measured clearance and used shim (shim that was removed) thickness, determine correct thickness of adjusting shim to be used. See Fig 1-19.
- On ES300, GS300 & SC300, shims are available in thicknesses of.0984-.1299" (2.50-3.30 mm), in increments of.002" (.05 mm). On GS400, LS400 & SC400, shims are available in thicknesses of.0787-.1102" (2.00-2.80 mm), in increments of.0008" (.02 mm). On models, using a micrometer, measure thickness of used shim (shim that was removed). Use the following formulas to determine how thick the new shim should be:
- Intake Valve: Subtract.008" (.20 mm) from the measured (actual) valve clearance. Add the result to the thickness of the used shim. The final result represents the thickness of the new shim.
- Exhaust Valve: Subtract.012" (.30 mm) from the measured (actual) valve clearance. Add the result to the thickness of the used shim. The final result represents the thickness of the new shim.
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.