The "X" heads have thicker port walls and can be ported much more than standard heads, I've been told. The outer casting and port profile from the factory are stock. Just the water jacket cores changed to make the port walls a bit thicker, apparently. On July 16, 2006 eddiestakes wrote: > What are these? I have had 3-4 sets of heads with X on them? > http://cgi.ebay.com/ebaymotors/AMC-X-Heads-V-8-block-RARE_W0QQitemZ14000 6635557QQihZ004QQcategoryZ34202QQrdZ1QQcmdZViewItem > Eddie Stakes' > Planet Houston AMX > 713.464.8825 > eddiestakes@xxxxxxxxxxxxxxxxxxxx > www.planethoustonamx.com ============================================================= Posted by wixList Archiver -- http://www.amxfiles.com/wixlist _______________________________________________ AMC-List mailing list AMC-List@xxxxxxxxxxxx http://www.amc-list.com/mailman/listinfo/amc-list or go to http://www.amc-list.com