103 engines are famous for oil consumption! Stem seals are a temporary fix ,you should check or have checked the valve guides for excessive wear.
If excessive wear is found the head will have to come off for repair. While the head is off check the cylinder bores, some engines never seated the rings and this can be confirmed by existance of fresh looking hone marks in the cylinders.
The tops of the pistons normally have oil ash deposits on them but if there is a clean area where the piston meets the cylinder the rings are pumping oil.
Good luck Mike