Ventiljustering

Ventiljustering, or valve adjustment, is the process of setting the clearance—valve lash—between the valve stem and the actuating elements (cam, lifter, and rocker arm) in an internal combustion engine. The goal is to ensure the valve opens and closes at the intended times and seals properly when closed. Appropriate lash varies by engine design, cylinder, and valve (intake vs exhaust) and is specified by the manufacturer.

Why it matters: too much lash can delay valve opening and reduce performance, cause a tappet noise, and increase wear. too little lash can prevent full valve closure, leading to valve burning, improper sealing, loss of compression, and potential engine damage. Valve adjustment is common in engines with solid or mechanical lifters; many modern engines with hydraulic lifters or self-compensating systems require little or no routine adjustment.

Methods: cold adjustment is performed with the engine cool, using a feeler gauge to measure clearance at the rocker or tappet; clearance is adjusted by loosening a locknut and turning the adjustment screw or installing shims. hot adjustments exist on some engines and occur with the engine warm. Many newer engines rely on hydraulic tensioners or lash adjusters that maintain proper clearance automatically, reducing maintenance needs.

Practical notes: always consult the service manual for correct lash values and procedures. Rechecking clearances after installation and ensuring correct timing marks helps prevent timing or piston-contact issues in interference engines. Signs of improper adjustment include ticking, rough idle, reduced power, or burning of valves.

See also: valve train, camshaft, rocker arm, feeler gauge, hydraulic lifter, valve timing.