hardened valve seats

[Darrell Norquay]

At 02:11 PM 8/18/96 +0000, Hans wrote:
>

>Does anybody of you know what (generally available) material
>I can use for unleaded-fuel-valve-seats? I am just working on an old
>motorcycle with aluminium head, which needs the valve seats to be 
>replaced. Could be X210 Cr Wo 12 the right thing? (I hope it's 

The material generally used in north american vehicles is called Stellite. 
I'm not sure exactly what it's chemical composition is.  These seats are
available as drop in replacements for standard seats, you simply machine out
the valve seat pocket in the head and press in the replacement seat.

BTW, for the information of the people asking about valve recession, it is
caused by high temperatures causing the valve to "spot weld" itself onto the
seat when the valve closes.  When the valve opens again, the spot weld is
ripped out of the seat, leaving a small pit.  The valve usually rotates in
the seat to even valve wear, thus as the spot weld/break process occurs all
around the seat, the net result is that the seat depth begins to increase.
The valve is essentially burning a hole into the head where the seat used to
be.  Leaded fuel eliminates this problem, as the lead coats the valve/seat
and prevents the welding process from occuring.

regards
dn
dnorquay at awinc.com