Here we go again....
Cooper S blocks have tappet chests the same as 998's ( aka small bores ), in general ( very general ) the block have more in common with small bores than they do with the stronger 1275 solid walled blocks.
When an engine is bored to +60, unless the bores are offset then there is little or no room left to overbore again to 73.5mm as the new bore may not cover the bore on the internal ( between pistons 2 and 3 ) side.. thus making it either very weak between 2 and 3 or not round !
The additional problem is the amount of metal between the bores is getting towards the limit and without the rigidity provided by the solid wall, there's a possibility that the block will basically fall apart under load.
Even the bible recommends not boring S blocks too far...
yep i thought that i had herd this somewhere recently, i can remember reading it in the David Vizard bible the other day.
http://www.theminifo...x...2522&hl=970
