Hydraulic vs. Mechanical Tappets: Which is Right for Your Engine

An automotive tappet, also known as a lifter, is a component of the engine that controls the opening and closing of the valves. The tappet is a small cylindrical part that sits between the camshaft and the valve stem. When the camshaft rotates, the tappet moves up and down, which in turn causes the valve to open and close. In this blog, we will take a detailed look at automotive tappets, their types, working principle, and maintenance.

Types of Automotive Tappets:

There are two main types of automotive tappets: hydraulic tappets and mechanical tappets.

1. Hydraulic Tappets: Hydraulic tappets are the most common type of tappets used in modern engines. They use oil pressure to maintain a constant clearance between the camshaft and the valve stem. Hydraulic tappets have a piston inside that is connected to the valve stem. When the camshaft pushes the tappet up, the oil pressure compresses the piston, maintaining a constant clearance between the camshaft and the valve stem.

2. Mechanical Tappets: Mechanical tappets are the older and more traditional type of tappet. They rely on a clearance adjustment mechanism to maintain the clearance between the camshaft and the valve stem. Mechanical tappets have a threaded adjusting screw that allows the clearance to be adjusted manually. When the camshaft rotates, it pushes the tappet up, which in turn pushes the valve open.

Working Principle:

The working principle of an Automotive Tappet is straightforward. The tappet is positioned between the camshaft and the valve stem. As the camshaft rotates, it pushes the tappet up, which in turn pushes the valve stem, causing the valve to open. When the camshaft rotates away from the tappet, the valve spring returns the valve to its closed position, and the tappet returns to its original position.

In hydraulic tappets, the oil pressure maintains a constant clearance between the camshaft and the valve stem. This ensures that the valve opens and closes at the correct time, without any clearance issues. Hydraulic tappets are quieter and require less maintenance than mechanical tappets.

In mechanical tappets, the clearance between the camshaft and the valve stem is adjusted manually using a threaded adjusting screw. This ensures that the valve opens and closes at the correct time, but it requires more maintenance than hydraulic tappets.

Maintenance:

Automotive tappets require regular maintenance to ensure that they function correctly. The following are some maintenance tips for tappets:

1. Check the clearance between the camshaft and the valve stem regularly. If the clearance is not correct, adjust it using the adjusting screw.

2. Change the engine oil regularly. The oil pressure in hydraulic tappets is crucial to their function, and dirty oil can cause problems.

3. Replace the tappets if they become worn or damaged. Worn tappets can cause valve clearance problems and lead to engine damage.

4. Check the valve train for wear and damage regularly. A worn or damaged valve train can cause tappet problems.

Conclusion:

Automotive tappets are a crucial component of the engine. They control the opening and closing of the valves, which in turn controls the combustion process. Hydraulic tappets are the most common type of tappet used in modern engines, while mechanical tappets are an older and more traditional type. Tappets require regular maintenance to ensure that they function correctly and do not cause engine damage.