Re: [alfa] Valve shims

[Mark Denovich <mark@xxxxxxxxxxxx>]

C M Smith wrote:

> Don't these have to be of hardened steel to resist the pressure of the 
> hardened cam faces? If so, then sanding them will take forever and be 
> counterproductive in that the subsequent wear will increase the 
> clearances pretty rapidly.
I think only the faces of the tappets (the upside down buckets) are 
hardened...  and they're not the part that gets sanded.   The shim sits 
under the bucket on top of the valve stem.   It should see near-zero 
wear since it doesn't really move against the underside of the tappet.

Of course if Alfa used a shim-over bucket design then it would be a 
completely different story.   1) the shim would almost certainly be 
hardened (although the bottom face could still be sanded I suppose) and 
2) they are generally much larger... like 1" in diameter.  They would be 
much more likely to crack due to grinding irregularities and the way the 
force of the cam is concentrated.

You can see a good picture here of a shim under bucket (although unlabeled)
http://www.centerlinealfa.com/products/images/pages/p4.pdf

--Mark
The Alfa Wiki: http://alfa.denovich.org
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