What is the specification for the intake valve clearance?
There is no single universal value for intake valve clearance. The exact specification is engine-specific and published by the manufacturer in the official service documentation. In many engines, the cold intake lash is in the narrow tenths of a millimeter range, but you must verify the exact figure for your particular engine and revision.
The basics: what intake valve clearance is
Valve clearance, or lash, is the small gap between the camshaft’s contact surface (such as a lifter or rocker arm) and the valve stem when the valve is closed. This gap accommodates manufacturing tolerances and thermal expansion so the valve seats properly as the engine warms up. If the clearance is too small, the valve can stick or burn; if it’s too large, you’ll hear clatter and lose precise valve timing.
Cold vs hot clearance
Most manufacturers publish the specification as a cold clearance measured with the engine at ambient temperature. Some engines also specify a hot clearance, which can differ due to thermal expansion during operation. Always follow the exact definition in your engine’s service manual and verify whether the value refers to cold or hot conditions.
Where the specification comes from
Engineers publish valve-clearance targets in the factory documentation that accompanies each engine family. The precise number depends on the engine’s design (SOHC, DOHC, number of valves, material choices, and whether the intake system uses shims or adjustable rockers). To ensure accuracy, mechanics and technicians consult the official sources tied to their exact model, year, and revision.
Before listing the sources, note that the following are the typical places to find the spec:
- Factory service manual (FSM) for your exact engine model, year, and revision
- Official repair guides and workshop manuals issued by the manufacturer
- Technical service bulletins (TSBs) and official repair information databases
- Authorized third-party databases that compile OEM specifications (e.g., Alldata, Mitchell1)
In practice, the exact clearance value can shift with engine revisions, market-specific calibrations, and parts substitutions. Always verify against the precise variant you are working on and consult the latest documentation.
How to determine and measure the intake valve clearance
Measuring valve lash requires careful procedure and the right tools. The following steps outline a general approach; specific engines may differ in sequence, tools, or whether shims are used for adjustment.
- Confirm the engine variant and obtain the exact clearance specification (cold and, if applicable, hot) from the FSM or official sources.
- Gather the proper tools: a set of calibrated feeler gauges (and any required shims or adjustment hardware), a torque wrench, and any engine-specific lifting or timing tools.
- With the engine in the appropriate position (often at or near the Top Dead Center for the cylinder being checked, following the manual), remove the valve cover or cam cover to access the valve train.
- For engines with adjustable lash, determine whether clearance is measured at the cam lobe/lifter interface or at the valve stem with the rocker. Use the recommended method from the manual and insert the correct feeler gauge to determine the gap.
- Compare the measured value to the specified cold (or hot) lash. If it’s out of range, adjust as required by the design of the valvetrain (shim changes or adjusting screws) and recheck each affected valve.
- Reassemble the cover, torque fasteners to spec, and, if applicable, run the engine and recheck the clearances once the engine reaches operating temperature (or as directed by the manual).
Accurate measurement and adjustment demand attention to the engine’s specific design. If you’re unsure or the procedure involves unfamiliar hardware, consult a qualified technician.
Key reminders about intake valve clearance
Remember that the clearance specification is engine-dependent and can vary by model year, market, and edition. Always use the exact value provided for your engine and follow the procedure outlined in the official documentation. When in doubt, seek professional assistance to avoid valve damage or improper seating.
Summary
Intake valve clearance is a highly engine-specific specification, not a universal number. The correct value is found in the manufacturer’s official service materials and may differ for cold vs hot conditions. To measure or adjust lash, follow the precise steps and use the proper tools for your particular engine, and verify the results by rechecking after cycling the engine. This careful approach helps ensure reliable valve seating, optimal performance, and long-term engine health.
