I am having my engine rebuilt and the head is being re-built and modified by someone who has built the heads for the mercedes race teams as well as various rally teams.
He is as high as i can get with regards to the building of this engine.

Now i need some info.

1) i need to know the "squish" clearence ????

2) i need to know the piston - valve clearence ????

3) i need to know the amount the head can be skimmed ????

Before when i have had engine work done i have taken the heads to have them "ported".
It just shows the difference of work this is about to recieve so your help with this is greatly appreciated.

Cheers in advance.

You should find answers to questions 2 & 3 in a Haynes manuel(book No.1948), as for No.1 I haven't a clue.  To be honest this kind of information is better found in books rather than on a fourm.  It might cost you a lot of money if they're wrong...! 

I've been modifying an M30 2.8i engine for the last few months, and belive me different people say different things, find someone who really knows what they're talking about, and if you trust them, then stick with them.  I've bought lots of books to help me with my engine, and I've learnt alot, it's the only way to really know whats going on under the bonnet!