There isn't a universal value—the correct valve clearance is engine-specific and set by the manufacturer in the service manual. It is typically specified as a cold clearance, and the exact intake and exhaust lash can vary widely between engines. Always refer to your exact engine's specification sheet for the correct numbers.
Understanding valve clearance and why it matters
Valve clearance, or lash, is the small gap between the valve stem and the rocker arm or lifter. This gap accommodates metal expansion as the engine heats up and ensures valves seal properly when hot. If the clearance is too small, valves may not fully close and could burn; if it's too large, performance may suffer and ticking noises can appear. Modern engines with hydraulic lifters often require no manual adjustment, while older or high-performance designs may use adjustable screw-and-locknut lash or removable shims.
Where to find your engine’s spec
The official specification comes from the factory service manual or workshop manual for your exact engine variant. If you don’t have a printed manual, check the manufacturer’s website, authorized service portals, or contact a dealer or qualified technician for the precise intake and exhaust lash values for your VIN/year/model.
Typical sources for the correct numbers include:
- Factory service manuals and technical bulletins specific to your engine family.
- Official workshop manuals published by the manufacturer.
- Quality repair guides that clearly cite the factory spec, used in conjunction with the manual.
Always verify the exact intake and exhaust lash for your engine variant, as specs can differ by model year and whether the engine is SOHC, DOHC, or has other valvetrain configurations.
Measuring valve clearance
Valve clearance is usually measured with the engine cold, though some engines specify hot measurements. The method varies by lifter type, so follow your manual when in doubt. The steps below outline a general approach that applies to many engines, but do not substitute for the exact factory procedure.
- Prepare the engine: ensure it is cold, disconnect the battery, remove the valve cover, and identify the cylinder you’ll work on.
- Rotate the crank to top dead center (TDC) on the compression stroke for that cylinder so the valve is closed.
- Use the appropriate feeler gauges to check the clearance between the valve stem and the rocker arm or lifter. Insert the gauge with a light drag; it should slide with noticeable resistance but not bind.
- Record the clearance for each valve (intake and exhaust) and compare to the factory spec for that valve.
Concluding: If all clearances are within spec, no adjustment is required. If any valve is out of spec, proceed to adjust or replace components as dictated by your engine design.
Adjusting valve clearance (when required)
Engine designs differ on how lash is adjusted. Some engines have hydraulic lifters that self-adjust and require no user adjustment; others use screw-and-locknut adjusters; some use removable shims. Follow the procedure that matches your engine and keep track of any shims or adjustments to avoid misassembly.
- For screw-and-locknut adjusters: loosen the locknut, turn the adjuster screw until the feeler gauge slides with a slight drag, then tighten the locknut while keeping the screw in place. Recheck the clearance for that valve.
- For shim-based (bucket) lifters: remove the cam cover, measure the current shim, and replace with a shim of the appropriate thickness to achieve the target clearance. Reassemble and recheck all clearances.
- For hydraulic lifters: if a valve is out of spec, the lifter or cam profile may be worn and may require replacement or more extensive service. Do not attempt to “adjust” hydraulic lifters beyond the manufacturer’s instructions.
Important: After any adjustment, rotate the engine by hand to ensure there’s no binding, recheck all clearances, reassemble the valve cover, and start the engine to listen for ticking or abnormal noises. If the specification includes hot-clearance values, perform a hot check after the engine reaches operating temperature.
Special cases: hot vs cold clearance
Some engines specify different lash values when the engine is hot. If your manual provides hot-clearance values, you’ll need to perform measurements after the engine has reached operating temperature or follow the hot-spec procedure exactly. Mismatching cold and hot specs can lead to valve timing issues or excessive wear.
When to seek professional help
If you’re unsure about your engine’s valvetrain design, lack the proper tools, or encounter stubborn wear, consulting a qualified mechanic is prudent. Engines with variable valve timing, advanced hydraulic systems, or rare shim configurations require precise procedures that are easy to misapply without the right instructions and torque references.
Summary
Valve clearance is not a one-size-fits-all specification; it is engine-specific and found in the factory service manual. Most engines use a cold clearance, with intake and exhaust lash values differing by valve type. Accurate measurement requires the right tools and procedure, while adjustment methods vary by lifter design—screw-in adjusters, shims, or hydraulic systems. Always verify the exact specs for your engine, and when in doubt, consult a professional to avoid valve damage or reduced performance.