"Dave Plowman (News)" wrote in message
...
To convert the cylinder head means machining the valve seats and pressing
in hardened steel inserts. The valves are also replaced with harder steel
items.

http://www.pumaracing.co.uk/unlead01.htm
--
Dave Baker
Resistance is useless (The Daleks)
Resistance is futile (The Borg)
Resistance is volts divided by amps (Georg Ohm)