soo, i've ran a search and i've read the tech section head info, so all A15 heads are oval port? no a12 heads are oval port besides the gx? or are later a12's (a12a) oval also?

what would be the main most common problems for overheating, took the dat for about an hours cane and it was quite hot weather but when i had finished temp was about 6/8 along on the temp gauge, it hasnt overheated on drives of this length before, usually stays on half. so any suggestions?