[Shotimes] adjusting valve lash by machining valve stems

[Donald Mallinson]

Ian,

This is a VERY BAD idea!  Here is why.

Those shims are hardened by a specific heating process. 
That hardening does NOT go all the way through.  By 
machining the shim, you cut through some if not all of the 
hardening.

I know, you can machine one side and put that side down, and 
that might work, but the finish on these shims is also very 
specific to the cam surface.  Would the machine shop be able 
to provide the EXACT finish that would help break in, but 
not destroy the lobe on your new cams?  if the finish is 
just a tiny bit more rough, there go your lobes.

Better to try to get correct new shims and do it right.

Don Mallinson

Ian Fisher wrote:

> I wanted to get the list's opinion on shimming valve
> clearances by actually machining down the valve stem
> instead of replacing shims. This was provided to me as
> an alternative method today. It sounded horrific at
> first but now that I think about it it doesn't seem
> like a bad idea. The clearances can be adjusted more
> accurately without the need to purchase any shims. The
> valve would still open and close normally...
> 
> My only issue is that I am installing +20's into my
> soon to be rebuilt heads. If I have the valves
> adjusted for those, I wouldn't be able to swap back to
> stock or +40's without using shims. Hopefully the
> shims could make up the difference.
> 
> I'm also installing bronze valve guides. The shop is
> going to machine the valve seats as well to make sure
> they are as good as they can get. They said that
> machining the seat will also tighten up my valve
> clearances. Interesting..
> 
> comments? 
> 
> Ian
> 
> 
> 
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