Valve spring squareness

[EngJW]

We have discovered that our exhaust valves are rapidly rotating on their own and wearing into the seats. They do not have rotators. We can obseve this with a strobe light.

We know that the springs are not ground very square and we are inclined to blame this. However, I am not convinced. When the valve opens it could rotate a few degrees in one direction, but on closing it should come back. Also, the rotation should occur while the valve is off the seat and should not cause the wear.

We have tried several material combinations, different spring loads, and different cam profiles.

Before we go and tighten up the tolerance and increase the cost, is there something I am failing to consider?

Thanks

 

[desertfox]

Hi EngJW
I have experienced a similar situation of compression spring rotating in service.
Speak to your spring manufacturer; from memory I was sent a copy of a paper from the spring research association regarding this problem which they refer to as "spring ratcheting", apart from preventing the spring rotating by physical means there's not a lot you can do to completely
prevent it, however you can minimise it by reducing the spring index ie:- redesign the spring or put a wear plate between the valve seat and the spring face if thats possible.

regards desertfox