These are special alloy* racing seats for enginies.

• The 46.35mm OD of these seats is 1mm larger OD than stock seats
• Oversize seats are not necessary for 45mm (1mm oversize) valves.  At 45.5mm stock seats are fine.
• Even 46mm valves (2mm oversize) are compatible with 45.5mm stock seats. The .25mm (.010") overlap is acceptable with the .5mm (.020") margin beyond the seat ring on the valve.

*Modified M2 Tool Steel, which utilizes a blend of three types of carbide materials to provide outstanding wear resistance for valve seat insert application.  Molybdenum and Tungsten carbides are both harder and more thermally stable than chromium carbides.  They also form a carbide structure to impart more stability to the base material.  Vanadium carbides are also added to provide greater wear resistance without affecting the machineability of the product.  This Iron based insert allows for excellent heat transfer.  T-series hardness run @ 42 Rc and is currently the industry choice when mated with premium or Inconel valves.

For more information about oversize valves and seats see section on "additional Prod Info"