Hello Arvid,
The correct model starter motor for a 1928 Chev is a Delco-Remy 710-D.The 714-L fits Chev's from 1929 to 1932,as well as 1933 & 1934 Std model 6 cyl Chev's.
The 710-C starter is the same as the 710-D,
except the 710-C is a Remy starter.With either the 710-C or D starter you can run an 11 or 10 tooth bendix pinion gear,as the flywheel ring gear has 110 teeth,all that changes is the cranking ratio,10:1 or 11:1.
With using the 714-L starter,the front
mounting housing that bolts to the flywheel housing is a different length from the barrel to the mounting flange,and the pinion gear could either not engage properly with the ring gear teeth,or engage too deeply,and smash off the pinion gear counterweight,as well as possibly damage the flywheel ring gear teeth.
Added to all this,you have a mechanically operated starter switch mounted on top of the 714-L barrel,which you would have to replace with a terminal stud to connect the field leads into,as well as your switch lead.
If the starter still turns over slowly,it probably needs an overhaul.The shafts on these can bend,as well the drive end housing bush wears out too.The commutator endplate has no bush originally,the shaft runs straight in the cast iron endplate,and if not oiled,as per the owners manual,it can wear badly as well.All this can lead to the armature "poling" ie.the armature rubs against the field pole pieces.
This will cause the starter to crank very slowly,as will leads of insufficient size.
