Originally Posted by Will @ M Developments
Standard exhaust cam is good for over 400. The inlet cam can benefit from a reprofile.
Valve springs can do the bigger power - however i personally would uprate them if you're doing high revs at that power.
Valves can do good power but exhaust valves may start to suffer from raised EGTs on top speed runs.
ST170 combustion chamer is 8cc smaller than a Zetec from memory so off the shelf 9.0:1 pistons tend to go over 10.0:1 with an ST head
Good info there cheers, might well start building my silly spec Zetec a little earlier. What are ST170 heads worth exactly? My mate has offered me one.