spit out shim?

[CharlieR]

I read about shims "spitting out" in this forum. I presume this means the rotation of the cam pops the shim out somehow. So what do people do wrong to cause this to happen? I don't want to make the same mistake when I do mine. eek!

 

[Yamaha V6]

Make sure the shim's seated properly in the bucket. Make sure it's the correct thickness, so you have the right clearance. That's about it.

 

[sdpatt]

Another mechanical malfunction that could cause the clearance between the cam lobe and tappet to increase to the point that the shim can be ejected is a problem with the valve or valve spring. If the valve binds in the guide or the spring fatigues or breaks, the tappet can separate from the cam lobe at times other than when the valve is fully closed. Fatigued springs or excessive engine rpms (8,500+) can allow valve "float" that prevents the shim from staying in contact with the cam lobe.

No matter what the cause, if the shin comes out of the tappet bucket, you will hear an unhealthy grinding, scraping, tapping noise from the upper engine area.

 

[CharlieR]

Yes, I get the picture that this is bad thing and would spell the demise of the camshaft and more and that I would hear "an expensive sounding noise" from the upper engine. I don't want to hear it and I just wanted to check to be sure I don't become the cause of it by making some mistake common to novices.
Thanks