In a message dated 5/5/99 7:47:50 PM Eastern Daylight Time,
mikeg@vicnet.net.au writes:
> This means the seat sealing becomes poor and directly burning
> mixture passes through the valve/seat gap, eroding the valve away.
> The seat would be less susceptible because of the far great thermal
> mass of the head.
>
The contact of the valve with the seat allows the transfer of heat away from
the valve. Therefore if valve clearances are insufficient the valve overheats
and burns. Intake valves are not as susceptible to this as the incoming
air/fuel mixture serves to keep them cool as well. If a piece of grit gets
between the valve and the seat the result is the same. Worn guides also
contribute to this problem as heat is also transferred away through the valve
stem to the guide.
Regards,
Peter S.
Charlotte NC
59 Bugeye
70 Opel GT
71 Midget
71 Fiat 850 Spider
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