Tappets

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Tappets

Editing Date：2026-04-11

Tappets (Lifters / Valve Lifters)

Tappets (also known as Lifters / Valve Lifters) are core transmission components in an engine’s valve train.

They are mainly classified into mechanical tappets and hydraulic tappets.

Core Classification Logic

•	By operating principle:
	Hydraulic Tappets
	Mechanical Tappets / Solid Lifters

•	By cam contact surface design:
	Flat Tappet
	Roller Tappet

•	By shape and structure:
	Bucket Tappet
	Mushroom Tappet
	Cylindrical Tappet

Mechanical Tappets / Solid Lifters

Key Features: Solid metal structure with no hydraulic compensation. Valve lash must be adjusted manually at regular intervals. Mainly used in high-performance / racing / vintage engines.

(1) Flat Tappet / Solid Flat Lifter

Structure: Flat or slightly crowned bottom surface with direct sliding friction against the camshaft. Available in bucket, mushroom, and cylindrical types.

Advantages: Simple structure, lightweight, high rigidity, no hydraulic lag.

Disadvantages: Requires periodic lash adjustment, tapping noise during operation, high wear rate.

(2) Roller Tappet / Roller Lifter

Structure: Equipped with a bearing‑mounted roller at the bottom, converting sliding friction into rolling friction, greatly reducing wear and power loss.

Advantages: Very low friction, long service life, excellent high‑RPM performance; preferred for racing / modified engines.

Disadvantages: Complex structure, high cost, relatively heavy.

Mechanical Tappets / Solid Lifters

Key Features: Solid metal construction with no hydraulic compensation. Valve lash requires regular manual adjustment. Widely used in high-performance, racing and classic engines.

（1）Flat Tappet / Solid Flat Lifter

Structure: Flat or slightly curved bottom surface with direct sliding friction against the camshaft. Available in bucket, mushroom and cylindrical types.

Advantages: Extremely simple structure, lightweight, high rigidity, no hydraulic lag.Disadvantages: Requires regular lash adjustment, tapping noise during operation, high wear.

（2）Roller Tappet / Roller Lifter

Structure: Equipped with a bearing‑mounted roller at the bottom, which changes sliding friction into rolling friction, greatly reducing wear and power loss.

Advantages: Very low friction, long service life, excellent high‑RPM performance; preferred choice for racing and modified engines.Disadvantages: Complex structure, high cost, relatively heavy weight.

Common Types by Outer Shape

(1) Bucket Tappet / Cup TappetStructure:

Cup-shaped or bucket cylindrical design, directly matched for overhead camshaft (OHC / DOHC) engines, the most common type for passenger vehicles.

Subtypes: Hydraulic bucket tappet, mechanical bucket tappet (including shim‑over‑bucket and shim‑under‑bucket types for manual clearance adjustment).

(2) Mushroom TappetStructure:

Mushroom‑shaped profile, mostly used in older OHV engines with an adjustment screw on top for valve lash.

(3) Cylindrical TappetStructure:

Hollow cylindrical shape for weight reduction, widely applied in medium and large diesel engines / OHV engines, available in flat and roller versions.

Core Types Comparison Table

Type	Core Principle	Clearance Adjustment	Running Noise	Application	Structural Complexity
Hydraulic Tappets	Hydraulic automatic compensation	Automatic zero lash	Very low	Mass-produced passenger car engines, daily vehicles	High
Mechanical Flat Tappets	Solid rigid transmission	Manual periodic adjustment	Tapping noise	Vintage engines, classic cars	Very low
Mechanical Roller Tappets	Roller-driven transmission	Manual periodic adjustment	Low	Racing, modified cars, high-performance engines	High

Additional Notes

Shim Tappet：

A subtype of mechanical bucket tappets. Clearance is adjusted by adding or removing shims on the top or bottom of the tappet. Widely used in older Japanese and European DOHC engines.

Rocker Arm Roller Tappet：

Integrates a roller into the rocker arm to replace traditional tappets. Mostly used in large-bore diesel engines and heavy-duty vehicle engines to further reduce friction.