GMC Envoy Valve Lifters Tappet

What is a valve lifter on the car?

Valve lifters tappets, commonly referred to as tappets, in the context of car engines. Valve lifters are components in an internal combustion engine that play a crucial role in the operation of the engine's valves. They are positioned between the camshaft and the engine's valve mechanism, and their function is to transfer the motion of the camshaft to the engine's valves. This transfer of motion allows the valves to open and close at the correct times in the engine's cycle, which is essential for the intake of air and fuel and the expulsion of exhaust gases, critical processes in the operation of a car's engine.

Types of valve lifters

• Hydraulic lifters: Use oil pressure for self-adjustment, found in most everyday cars for quiet and maintenance-free operation.

• Mechanical lifters: Require manual adjustments to maintain valve clearance, often used in high-performance and racing engines for precise control.

• Roller lifters: Feature a roller wheel for reduced friction, ideal for high-performance engines and racing, enabling aggressive camshaft profiles and high RPM operation.

• Needle bearing lifters: Some roller lifters use needle bearings for added durability, commonly used in high-performance and racing engines.

• Direct-acting hydraulic lifters: Combine hydraulic self-adjustment with precise control, often found in high-performance and sports car engines.