What cylinder heads are these ?

How do you tell the difference between a ST70 cylinder head & an overhead cam C90 cylinder head ?

I have two bare heads....one has markings E8 and has a combustion chamber diameter of about 45mm ....... the other is marked E16 and has a combustion chamber diameter of about 39mm.

Thanks.... Steve.

OT50 heads have a combustion chamber of 39mm. (6v: c50, ss50, st50, z50,...)
OT70 and C90 are 47mm.

C90 valve in: 18mm / valve out: 16mm
OT70: 25mm / 22mm
OT50: 19mm / 16mm

Thanks Waynus.