As long as the minimum thickness at the edge of the valve is not violated, nothing bad. My brother did the machine work on the heads of my 1.9l about 140k miles ago. Nothing bad has come of grinding the exhausts. Now, he did take minimal cuts on all the valves - just enough to get a straight seat. We did that on the valves and on the heads. It amounted to just a little more than a "hard" lapping, IIRC. Not alot needed to be done. I was glad for that, because exhaust valves are the very devil to lap by hand, because they are such a hard metal. BTDT!

"Giasson, Pascal (DNR/MRN)" <Pascal.Giasson@GNB.CA> wrote:  I just got a valve job done on my 1.9 heads from a machine shop. I gave
them the Bentley and showed them where it says not to grind the exhaust
valves. They said they have reground exhaust valves many times for the
local VW mechanic and this was the first time they were made aware that
VW says not to grind them. I thought they were just going to lap them
as per the Bentley, but the machinist said they needed to be ground so
that is what he did. Does anyone know what will happen to a ground
exhaust valve? Thanks

Pascal

'84 Westy