Here are a couple pics of my cylinder head.
The 71 cc chamber has been laid farther back to increase the airflow. They were @ 65 cc" IIRC.
The other pic,chamber has not been opened up yet.
Just don't go past where the head gasket seals to the block.
Use blue dykum (SP) @ scribe a line where the head gasket edge is.
Don't get too carried away,,but his will give you an idea how to correctly get more airflow by laying the chamber wall back.
MBHD
