hi - i'm told that on a standard yb cosworth engine the pistons protrude form the block slightly? would this mean then, that in the event of cam belt snapping or incorectly set up cams that the pistons would hit the valves?

the reason i ask is cos i'm building an engine to 7.2 cr using flat top pistons which will need machining to get cr correct and calculations show that pocketing the pistons instaed of simply facing them would be possible and would accomodate such an event.

any ideas???