Valve stems made completely out of peek or delrin?

[hpmr2400]

Just some thoughts popping into my head, has anyone out there ever made a poppet and stem completely out of these plastics? Would the stem hold up against the hammer strike over time? Would be a interesting experiment.
 Anyone every try it?

[Rallyshark]

I think a valve stem made of Derlin would be a lost cause.  PEEK may have a chance, but I think it would also fail.  PEEK is great for a valve seat or poppet, but I don't know that I'd trust in a valve stem situation?  I'm speaking generically, of course

[mann]

Matt has made a peek poppet maybe he'll chime in on the subject

[Rob M]

mild steel barely holds up , hardened steel takes some abuse, so I don't think a plastic would hold up unless the closing force of the valve was close to zero.. just my opinion

[hpmr2400]

Well, how about the new balanced valves that are coming out, it takes less force to crack them open.picture a full poppet and stem made of PEEK.. and say if you used a lightweight mds hammer. Wonder if it would hold up then?

[ackuric]

I've used peek as poppet material but not as a stem and wouldn't necessarily recommend it, even though I've taken the stock stem down to .045" in OD and a HSS drill bit blank stem down to .04" and have yet to fail either, but my valve is very easy to crack open and regulated so the stress on my stems are minimal...so possibly a .125" peek valve stem would work in one of the balanced/force reduced valves but I am not sure I'd trust it in a near-stock setup.

I'd want the densest material possible like carbon fiber nano tube as to minimize flex which would consume energy from hammer strike if I were to opt for a non-metal based valve stem. I prefer to thin mine down as much as reasonably possible to allow better air flow around the stem, a stock .125" stem centered into a .213" stock throat allows only .044" space from the top of the stem to the top of the valve exit port which means a lot of air has to work around the stock stem. With my .04" stem in my .225" throat I have .0925" space between the top of my valve stem and the exit port which IMO allows a bit better flow. I could be wrong.  The air also has to work "around" the .125" stem which is less aerodynamic than a .04" stem as there is less drag going across it. Minimal as it likely is I still prefer it and have seen some manufactured valve stems with reduction in the same area that is within reason for the forces applied to the poppet itself.

-Matt

[Motorhead]

In no way stiff enough a material in such a small diameter being far too compressible over the length it would be. 
Trick with peek is when used as a poppet / seat material it has very little compression yield allowing the kinetic strike of the hammer on the STEEL poppet stem to lift the peek seat with minimal energy loss.   
IMO having the entire length of poppet valve being the Head / Stem, you will get cumulative compression & deflection over such a long distance effectively negating the benefit of the materials use as originally engineered.

JMO ... 

[oldpro]

 Absolutely no chance any plastic with that small a diameter would hold up under any circumstance. And if you made it thick enough to work the closing force of the stem diameter would make the dwell so short you couldnt make any power at all even with a balanced valve. Stick with drill rod there are better ways to get the job done. 

[MJP]

Just one question, why would you use peek for the stem? I cant think of any reason.

Marko