Re: valve adjustments

[Einar Sjaavik <einar@ski.mail.telia.com>]

> shims different?  a guy told me you can rub a shim on a flat surface like
> glass and real fine sandpaper, to reduce its thickness. are they surface
> hardened? can this work?

I have not done the Alfa yet, but FWIW the similar Maserati shims can be
ground.
What I did was to order the thickest there is. Then after measuring,
I sorted the old shims to places where they would be just too thick and
noted how much they needed to be shaved (if at all). That left me with 
some that had to replaced because they were too thin, and I noted the 
thickness I needed for these too.

Then I put a 10mm slot mill chuck in the headstock of the lathe. The
shims were 10mm outside dia and fit very well with no wobble. Then
the support grinder was used to shave off what was needed on each shim.
Quick and easy. Now you may not have these tools but check around,
maybe someone that has can do it for you. It doesn't take long.
You may ask over at rec.crafts.metalworking if there is someone near
you with these tools.

And yes, fine tuning can be done on emery paper. But don't take too
much as you can easliy grind it to a wedge. When measuring thickness
with a micrometer, try to turn the shim. If it is not wedged, it will
have no preference for a centre point of rotation. If it is wedged
it will rotate around the thickest point.

When re-using shims, don't select them on the thin side. They will have
some wear pattern on the inside where you cannot easily grind them.
This wear pattern will not match the one on another valve and will
settle down a tiny bit, opening the clearance. If you have ground the
valves and seats, they will also settle, and close the clearance.

After it's all done, note down the thicknesses of the shims on a sticker
and place it where it can be found the next time an adjustment is due.
Then you can order shims before taking out the cams.

-- 
Einar Sjaavik, einar_sjavik@login.eunet.no,
http://www.login.eunet.no/~einar/
1986 Alfa GTV 2.0, 1986 Maserati Spyder 2.5, 1974 Mini 1000, 1952
Ferguson TEA