Technical Information
Engine Valve Nomenclature
Most engine valves are designed as poppet style valves because of their up and down popping motion and feature a conical profile valve head that fits against a machined valve seat to seal off the passage of fluids or gases. They are also called mushroom valves because of the distinctive shape of the valve head. Figure 1 shows the nomenclature for the different elements in a typical engine valve.
Diagram showing the nomenclature of a poppet valve.
Figure 1 - Nomenclature for a standard poppet style engine valve.
The two primary elements are the valve stem and the valve head. The head contains a fillet that leads into a seat face that is machined at a specified angle to match the machining of the valve seat to which it will match. The seating of the valve face to the valve seat is what provides the seal for the valve against combustion pressure.
The valve stem connects the valve to the mechanical elements in the engine that operate the valve by creating a force to move the stem against the seating pressure provided by a valve spring. The keeper groove is used to hold the spring in position, and the tip of the valve stem is repeatedly contacted by a rocker arm, tappet, or lifter that actuates the valve.
Figure 1 - Nomenclature for a standard poppet style engine valve.
Engine Valve Nomenclature
Most engine valves are designed as poppet style valves because of their up and down popping motion and feature a conical profile valve head that fits against a machined valve seat to seal off the passage of fluids or gases. They are also called mushroom valves because of the distinctive shape of the valve head. Figure 1 shows the nomenclature for the different elements in a typical engine valve.
Diagram showing the nomenclature of a poppet valve.
Figure 1 - Nomenclature for a standard poppet style engine valve.
The two primary elements are the valve stem and the valve head. The head contains a fillet that leads into a seat face that is machined at a specified angle to match the machining of the valve seat to which it will match. The seating of the valve face to the valve seat is what provides the seal for the valve against combustion pressure.
The valve stem connects the valve to the mechanical elements in the engine that operate the valve by creating a force to move the stem against the seating pressure provided by a valve spring. The keeper groove is used to hold the spring in position, and the tip of the valve stem is repeatedly contacted by a rocker arm, tappet, or lifter that actuates the valve.
Engine Valve Specifications
Typical engine valves are specified by the parameters outlined below. Note that this data is intended for information purposes and be aware that variations in the parameters used for specifying engine valves may exist from manufacturer to manufacturer. By understanding the specifications, buyers are better equipped to engage in discussions of their specific needs with suppliers of engine valves.
- Stem diameter – the diameter of the engine valve stem
- Stem length – the distance from the stem tip to the valve head
- Seat angle – the angle cut of the valve head’s seat, measured in angular degrees, typical values being in the range of 20o – 60o
- Valve materials – describes the material or materials used for the valve fabrication
- Coatings – identifies any coatings or surface treatments applied to the base material of the valve, such as chrome plating, nitride, PVD, or ceramics, for example
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