Valve Seat Inserts for American Diesel & HD Gas engines
The valve seat insert is the primary medium which receives and dissipates the heat from a red hot exhaust valve. It bears up well even in severe duty applications
In early engines valves closed directly onto the ductile iron cyl head or cyl block casting without seat inserts. Additionally those engines had limited intake filtration and standard duty valves resulting in periodic valve grinds. Valve seat inserts in later engines were induction hardened or case hardened in the block (side valve) or cylinder head (OHV).
In today’s engines the demands are quite different:
a) Higher horsepower with little change to engine bore size
b) Higher combustion temperatures due to emission control laws
c) Tighter working tolerances
d) Stronger valve springs and engine braking
e) Changes in fuel chemistry and coolants
With the advent of these changes, component manufacturers in collaboration with the engine maker had to rise to the challenge. Through advanced research and exhaustive testing, today’s valve technology & seat metallurgy offers substantially more thermal cycles and longer service life. Concurrently, valve seat wear has been reduced with air filtration efficiency in the vicinity of 99.95%+ and lower sulphur content in diesel fuel. Heavy Duty gas engines use special composition inserts which meet or exceed the OEM requirement to provide a good service life.
Valve Seat Inserts are manufactured from various materials including iron, nickel, tungsten and cobalt base alloys. Materials used in valve seat inserts are equivalent to or exceed the OEM product and offer good machinability. Most intake inserts are made from high grade iron, silchrome and nickel base alloys. Exhaust inserts comprise nickel base, non-magnetic or tungsten/cobalt base alloys.
Traditionally, good quality valve seat inserts are selected on a ‘size for job’ basis. Certain models including high horsepower variants use parts which are application specific. Engine valves and valve seats in these instances with their intrinsic built-in features are ‘married’ by part number for their dedicated use as engineered by the manufacturer.