Nope, the modification on the head is made to make more turbulent the mixture, lowering the Combustion head height is to regain the lost compression due to the slightly larger volume on the combustion chamber.

Look at the post I put to a magazine and see the website that someone posted on the first replies.

Sorry for reviving such old thread, but like many others buried here contains lots of good information. Maybe MXwrench and some others may look for those and put a sticky thread just for info, seems that many people are here for wrenching their own engines and look for information.