All Topics  
Hydraulic lifters

 

 
   Email Print
   Bookmark   Link
 

 

Hydraulic lifters
 
 
  Topics Hydraulic lifters Topic Home

A hydraulic lifter, also known as a hydraulic tappet
Tappet

A tappet in mechanical engineering is a projection which imparts a linear motion to some other component within an assembly. Properly speaking, a tappet is only that part of a rocker arm which makes contact with an intake or exhaust poppet valve stem above the cylinder head of an internal combustion engine....
 or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. The conventional means of adjusting valve
Poppet valve

A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem....
 actuation always requires a small clearance to be left between the valve and its rocker or cam follower to allow for thermal expansion and wear. The hydraulic lifter was designed to ensure that the valve train always operates with zero clearance, leading to quieter operation and eliminating the need for periodic adjustment of valve clearance.

The hydraulic lifter consists of a hollow expanding piston situated between the camshaft and valve.






Discussion
Ask a question about 'Hydraulic lifters'
Start a new discussion about 'Hydraulic lifters'
Answer questions from other users
Full Discussion Forum



Encyclopedia


A hydraulic lifter, also known as a hydraulic tappet
Tappet

A tappet in mechanical engineering is a projection which imparts a linear motion to some other component within an assembly. Properly speaking, a tappet is only that part of a rocker arm which makes contact with an intake or exhaust poppet valve stem above the cylinder head of an internal combustion engine....
 or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. The conventional means of adjusting valve
Poppet valve

A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem....
 actuation always requires a small clearance to be left between the valve and its rocker or cam follower to allow for thermal expansion and wear. The hydraulic lifter was designed to ensure that the valve train always operates with zero clearance, leading to quieter operation and eliminating the need for periodic adjustment of valve clearance.

The hydraulic lifter consists of a hollow expanding piston situated between the camshaft and valve. It is operated either by a rocker mechanism, or in the case of one or more overhead camshafts , directly by the camshaft. The lifter is filled with engine oil intermittently from an oil galley via a small drilling. When the engine valve is closed, the lifter is free to fill with oil. When the valve is opening and the lifter is being operated by the camshaft, the oil feed is blocked and the lifter acts just as a solid one would, oil being incompressible.

History

The first firm to include hydraulic lifters in its design was Pierce-Arrow
Pierce-Arrow

Pierce-Arrow was an United States automobile manufacturer based in Buffalo, New York, which was active between 1901 and 1938. Best known for its expensive luxury cars, Pierce-Arrow also manufactured commercial motor truck, Fire apparatus, camp trailers, motorcycles, and bicycles....
 in the early 1930s. Hydraulic lifters were popular on automobile
Automobile

An automobile or motor car is a wheeled motor vehicle for transportation passengers, which also carries its own car engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally f...
s designed in the 1980s, but most newer cars have reverted to bucket-and-shim mechanical lifters. Although these do not run as quietly and are not maintenance-free, they are cheaper and rarely need adjustment because the wear caused by operation is spread over a large area.

Disadvantages

There are a number of potential problems with hydraulic lifters. Frequently, the valvetrain will rattle loudly on startup due to oil draining from the lifters when the vehicle is parked. This is not considered significant provided the noise disappears within a couple of minutes, typically it usually only lasts a second or two. A rattle that does not go away can indicate a blocked oil feed or that one or more of the lifters has collapsed due to wear and is no longer opening its valve fully. The affected lifter should be replaced in the latter circumstances. In extremely rare circumstances, a lifter can "pump up" and create negative valve clearance so that its valve cannot close. This is more serious as burnt valves will result. In all cases it is important to follow the manufacturer's recommendations for oil viscosity
Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
 and quality.

External links