3 angle valve job.
Actually the exhaust flows much less than the intake. so porting and /or larger valves help in that area.
This is a great article to read on the B13 GA
http://www.mathermotorsports.com/html/timmotor.html
The valves are small and the springs will have float issues at higher RPM's. The valves also have a small shaft diameter so I was reluctant to back cut and unshroud the stockers for fear of weakining them too much. I would say Ferrea would be a good candidate to make a new set of valves.
The weakiness that Bob found was the connecting rod bolts, time will tell how the bearings hold up.