The valve seat is a critical component of the engine. It is necessary for thermal management and ensuring the mechanical efficiency of the engine. It’s main function is the regulation of temperature in the valve. It transfers heat from the valve to the cylinder head, and then to the cooling water circuit. This makes the valve seat and parts like valve seat inserts, extremely critical, especially in high performing engines like race car engines.

Race engine builders are constantly working with valve seat inserts to ensure longevity and a higher ability to withstand the heat generated in the engine. From sprayed valve seats to hollow-stemmed valves — many designs have been attempted to achieve this objective. Sometimes valve seat inserts are machined and fitted on site.

Failure of the valve severely affect the working of the engine. It can cause overheating, leading to faulty performance. But why do valve seats fail? What can you do to ensure that the seats keep performing optimally? The first step is to understand the common reasons behind valve seat failures:

Material failure

One of the most common reasons for valve seat failure is material failure. Give the high heat generated in the valve, the material must be able to withstand the heat and pressure without losing its integrity. It must also have superior wear strength, given the corrosive environment and abrasions. The common material used for making valve seats are copper alloys. Cast iron valve seats are also highly preferred.

Today we also find plastics like PTFE in building valves. However, metallic valves like copper and cast iron gives us better functionality because these metals have higher thermal conductivity, better wear resistance and strength. They can withstand the big heats generated in the valve, while keeping their form intact. The metallic valves also have better wear resistance, retaining their shapes and less susceptible to scratches and abrasions. A recent practise is to use nickel and chromium casted valve seats. These two elements improve the thermal conductivity and wear resistance of the valves.

Faulty design and installation

The valve seat insert needs to be designed carefully. It must be compatible to the function and the environment. If the valve insert does not work, the valve will start malfunctioning very soon. The consequences could be a small leakage to the failure of the entire engine. The design has to take into account the installation as well. All too often faulty design with bad installation results in the breakdown of the whole engine.

Some valve seat installations also need special technique or procedure. In installation where we expect high-pressure conditions, the valve installation follows a pattern where the valve is actuated repeatedly. The intention is to deliberately cause deformation. It is then rebuilt and set as per the parameters. This initial deformation method is necessary to ensure long-long-term efficiency of the valve. However, when the procedure is not followed, the valve seat may work fine in the beginning, but will soon start to fail. The fault will occur due to faulty installation and not the manufacturing.

Poor machining

Valve seats have to be very precise. Their function is to fit in place without leaving any scope for the escape of compressed gases. This kind of precision is only possible with machining. Poor machining can result in inadequate fit that will come loose with time. This is why in high performing engines like race cars, the valves seats are machined on site.

Wrong selection

Valve seats are not one-size-fit-all. The type, size, material and even the installation will depend on the functioning and environment of the valve. Ignoring these parameters can cause catastrophic failures. For instance, if we don’t take into account the temperature and pressure spikes, the valve will not be able to cope with any rise in these elements. Some may fail immediately, while others will last for only a short time.

Corrosion and friction

The corrosion of the valve is inevitable, given the high pressure and temperature working conditions. The surface will slowly corrode, leaving the valve seat less than effective. But there are also conditions where excessive torque requirements cause greater friction. This happens when we use excessive circumferential force to seal the valve. This increases torque requirements and leads to high friction. The valve gets locked in position. Eventually the valve seat insert may even disintegrate.