Honda raised deck flathead likely has a custom valve installed .
Head size , stem length and diameter would be needed info .
A custom or modified valve may be nessacery .
Mcgee , Rhino , Arc , Dyno Cams . Maybe Brian Carlson would have some info .
The builders are getting few and far between with age as is the engine .
Pm Stevevaughn31 he might be the most helpful .