I was told that the 87cc heads run a shorter valve as the seats are "sunken" somewhat in the chamber to increase the volume, hence how they get 87cc's out of a 72cc head.
Someone may wish to correct me if i'm wrong, but it is what I was told in a thread about a month ago. It seems very logical not to have 2 different castings, but to just machine it differently.
Hope this helps
__________________
'71 Holden HQ Monaro - 3850lbs race weight, 400c/i - 11.4 @ 120
'66 Pontiac GTO - 389, 4 speed street cruiser
|