Guide

Valve Lifters – What Should You Know?

Valve lifters, also known as self-adjusters or colloquially as “tappets”, are designed to maintain the correct valve clearance at any point during the engine’s operation. In older designs, they were equipped with adjustment screws, which allowed for setting the appropriate valve clearance (0.05-0.5mm). In newer designs, hydraulic self-adjusters are most commonly used. This is a maintenance-free system in which oil pressure helps compensate for clearance during engine operation. Unfortunately, this system has its drawbacks, being very sensitive to the quality of oil and contamination. If deposits get into the lifter hole, it can become blocked, causing the valve not to close properly, resulting in a loss of compression.

Consequences of incorrect valve clearance:

• If the clearance is too large, it accelerates the wear of the upper surface of the valve along with the cam lobes. This damage is characterized by a distinctive metallic tapping noise, which may disappear after the engine warms up.
• If the clearance is too small, it results in the valves not closing properly, meaning reduced engine compression (loss of power, uneven operation). This leads to faster wear of the valves.