Stellite Seats

The whole unleaded question regarding valves is a bit tricky to explain. To begin with certain 'older style' engines can run perfectly satisfactorily on plain 214N material, due to the fact that they are not a modern day 'lean' burn, high revving engines, expected to do modern day mileage and service intervals.

Unfortunately every engine is different. What we have found is that if the cylinder heads have had modern day ‘unleaded’ hardened seat inserts fitted the seat insert will most probably be too hard for the valve which could excessively wear the valve seat. In this particular case we would recommend a stellite seated exhaust valve.

For racing use unless the engine is a very heavily loaded engine or has forced induction you could usually get away with 214N or 1.4882 material as the valve will not be in service as long as a standard road going valve.

As a rule of thumb any exhaust valve running on modern day fuels should NOT be magnetic, if so, it is a martensitic (magnetic) steel which nowadays is used as inlet valve material. 214N which is an austenitic (non magnetic) stainless steel developed in the 60’s and designed to run on leaded fuel. Some older style engines pre 60’s used EN54 (non magnetic) steel some with a stellite 6 seat or EN59 / EN52 both of which are magnetic materials. Any of these materials would not be as good as a plain 214N exhaust valve. The addition of stellite seats has been implemented due to the demise of leaded fuel leading to excessive seat wear.

The other thing to note is that 214N (austenitic stainless steel) is not compatible to run in cast iron guides without a surface treatment on the stem e.g.: plasma nitride, chrome or tufftride, where EN52 or inlet (magnetic) material without a treatment is acceptable. Nimonic 80A is also not compatible to run with cast iron guides without a surface treatment on the stem e.g.: plasma nitride or chrome, but is acceptable to use unleaded fuel without a stellite seat

The basic procedure for a Stellite Seat Valve Forging is as follows:

	1. Forge a forging as per normal procedure
	2. Tracking of forging (to be able to deposit a layer of Stellite No.6)
	3. Welding of the Stellite Deposit on the forging
	4. Coining of forging (drives the stellite in to the base material) and removes any porosity in the stellite layer.
	5. Section sample forging to determin correct position of the stellite