Steve,
A couple of thoughts;
The height of a valve head above it's surrounding surface is determined
by original machined depth of the seat, & the valve head margin. (extra
distance between the valve seating angled cut & the top of the valve).
Different factories & rebuilders use different dimensions & some valves
have more margin than others to start with. This margin is intended to
allow for a clean up valve reface or two before the margin becomes nil &
the sharp edge starts burning. The seat also has dimensional allowances
for regrinding, which deepens the seat. Without knowing the original
projection (height) of your valve tops before the "test period" it is
impossible to say how much valve seat recession you might have had.
Certainly comparing your head to a different head would give no real
evidence either way.
Valve seat & valve face pitting is a natural result of high temperature
metal oxidation. (Flame erosion) It has no effect on valve sealing
unless it is really severe. Lead has no effect on pitting. Pitting can
be reduced by using a more high temp. oxidation resistant material for
the valves & seats. Some racers use the more exotic valve & seat
materials, but they are running for extended periods at very high engine
loads & exhaust valve temperatures.
It is always to the shops financial advantage to do as much work as
possible.
Dave Russell
BN2
BJ8Healeys wrote:
> Hello, Healeyphiles -
> I asked my rebuilder about unleaded mods to the head. He showed me the
> difference between the valves as they were installed in my head, and those of
> another (non-Healey) engine, and said that I had significant valve recession.
> When the valves were removed, I could see significant pitting of the seats.
>
> Happy Healeying!
> Steve Byers
> HBJ8L/36666
> BJ8 Registry
> Havelock, NC USA
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