hello peeps need help!!!!!!!!

just built a 1.8 16v zetec turbo engine

problem is after having cambelt fitted (engine out of car on engine stand) I have found out that after turning the engine over manually with a spanner on the bottom pully,that the pistons are hitting the head

have removed cambelt & camshafts so to make sure that its not the valves,but it still hits the head

bottom end turned ok before head was put on,pistons did hang out of block at T.D.C did'nt really think much of it as standard pistons stick out by apx 0.5mm,
been told that pistons should be 2mm below block deck at T.D.C with a comp ratio of 8.2.1?????????????
could anyone offer some pointers,advice point me in the right direction!

the pistons are forged accralite crowns have been machined to achive 8.2.1 compression ratio,standard 1.8 mondeo head gasket (was recommend to use it!)

any help would be GR8