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How do I find out whether a valve is nimonic or stainless steel ?

Wim

Apart from asking the manufacturer, I can't think of a way. Both are non magnetic, hard & shiny. I would have thought that very, very few new valves for A series engines would be Nimonic of any grade nowadays.

Thirty five years ago i bought a modified head, and never came to it to use it. I recently took it apart and noticed that both inlet and exhaust are non magnetic.

Wim

Only way of being sure is by checking end of valve for any markings. This may tell you if they are nimonic grade

Generally, Stainless Valves are one piece and 'Nimonic' are 3 piece, they usually have a Stellite Tip. If you look very closely at the tips, you may see a different material inserted in to the tip.

The stellite tip is an excellent tell tail. I wish I had thought of that one

Picture??

Did the nimonic valves loose out to the stainless steel valves for racing/rallying applications ?

Is it equally hard to machine the seats or is the nimonic some what softer ?

Wim

I don't have one to hand, & doubt I'd be able to take one that showed the difference. The stellite tip on an original S valve can usually be seen as the stellite is just a little shinier or "brighter".

I think that Stainless won out because it was cheaper & you could make 1 piece valves with it.

mk1 wrote: I think that Stainless won out because it was cheaper & you could make 1 piece valves with it.

Yes, Nimonic Vlaves are considerably more expensive (at least to manufacture, what happens at the counter maybe a different story though).

How can I tell where the Nimonism is?

Looks like a regular valve to me.

I agree the shape looks quite regular, save for the rounded edge of the exhaust valve. The trickery is apparently in the combination of strength, heat capacity and heat conductivity at working temperatures.

The stem, valve and the tip are all non-magnetic

Wim

Hard to tell for sure from those pics (it is something that's very difficult to captuture) but that does appear to be a Stainless Valve.

The Originals from the factory also had their Part Number in the Stem, if I recall right, just below the Collet Goove.

I'll see if I can dig out an S Valve and hopefully get a pic up.

Spider wrote:
The Originals from the factory also had their Part Number in the Stem, if I recall right, just below the Collet Goove.

I took bout 10 shots of the tip to try to show the Stellite Tip, however, my Photograph skills are well short of the task.

As Mark said a few posts back, the Stellite Tip is shiny. If you clean the valve, the stem will look like bright steel, however the tip will look better than Chrome Plating.